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	<id>https://medicalware.org/w/index.php?action=history&amp;feed=atom&amp;title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0</id>
	<title>常用対数 - 版の履歴</title>
	<link rel="self" type="application/atom+xml" href="https://medicalware.org/w/index.php?action=history&amp;feed=atom&amp;title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0"/>
	<link rel="alternate" type="text/html" href="https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;action=history"/>
	<updated>2026-05-03T20:22:01Z</updated>
	<subtitle>このウィキのこのページに関する変更履歴</subtitle>
	<generator>MediaWiki 1.39.0</generator>
	<entry>
		<id>https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5293&amp;oldid=prev</id>
		<title>imported&gt;Mono Book: /* 定義と概要 */</title>
		<link rel="alternate" type="text/html" href="https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5293&amp;oldid=prev"/>
		<updated>2014-10-29T10:15:39Z</updated>

		<summary type="html">&lt;p&gt;&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;定義と概要&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;ja&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← 古い版&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;2014年10月29日 (水) 19:15時点における版&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l18&quot;&gt;18行目:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;18行目:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;底の変換公式  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039;)  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;a&amp;#039;&amp;#039;) = log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; によれば、常用対数の値は同じ数を真数とする[[自然対数]]の log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;e&amp;#039;&amp;#039; = 約 0.43 倍の値を示す。&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;底の変換公式  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039;)  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;a&amp;#039;&amp;#039;) = log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; によれば、常用対数の値は同じ数を真数とする[[自然対数]]の log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;e&amp;#039;&amp;#039; = 約 0.43 倍の値を示す。&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;*&lt;/del&gt;[[水素イオン指数]]&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;（&lt;/del&gt;[[pH]]&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;）&lt;/del&gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;==例==&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;*&lt;/del&gt;:&amp;lt;math&amp;gt;\mathrm{pH} =-\log_{10} \frac{[\mathrm{H}^+]}{\mathrm{mol/L}}&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;===水素イオン指数===&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;[[水素イオン指数]]&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;（小中学校では&lt;/ins&gt;[[pH]]&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;として習うはず）は常用対数で表されている。&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;:&amp;lt;math&amp;gt;\mathrm{pH} =-\log_{10} \frac{[\mathrm{H}^+]}{\mathrm{mol/L}}&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;:例えばpH 6.0とpH 5.0の見かけ上の差は1.0だが、実際のアルカリ性の度合いで言えば10倍の差がある。&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;:同様にpH 6.0とpH 4.0の見かけ上の差は2.0だが、実際のアルカリ性の度合いで言えば100倍の差がある。&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;== 常用対数表 ==&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;== 常用対数表 ==&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;

&lt;!-- diff cache key medicalware-mw_:diff::1.12:old-5292:rev-5293 --&gt;
&lt;/table&gt;</summary>
		<author><name>imported&gt;Mono Book</name></author>
	</entry>
	<entry>
		<id>https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5292&amp;oldid=prev</id>
		<title>imported&gt;Mono Book: /* 定義と概要 */</title>
		<link rel="alternate" type="text/html" href="https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5292&amp;oldid=prev"/>
		<updated>2014-10-29T10:07:41Z</updated>

		<summary type="html">&lt;p&gt;&lt;span dir=&quot;auto&quot;&gt;&lt;span class=&quot;autocomment&quot;&gt;定義と概要&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
				&lt;col class=&quot;diff-content&quot; /&gt;
				&lt;tr class=&quot;diff-title&quot; lang=&quot;ja&quot;&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← 古い版&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;2014年10月29日 (水) 19:07時点における版&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l18&quot;&gt;18行目:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;18行目:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;底の変換公式  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039;)  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;a&amp;#039;&amp;#039;) = log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; によれば、常用対数の値は同じ数を真数とする[[自然対数]]の log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;e&amp;#039;&amp;#039; = 約 0.43 倍の値を示す。&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;底の変換公式  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039;)  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;a&amp;#039;&amp;#039;) = log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; によれば、常用対数の値は同じ数を真数とする[[自然対数]]の log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;e&amp;#039;&amp;#039; = 約 0.43 倍の値を示す。&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;*[[水素イオン指数]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;*[[水素イオン指数]]&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;（[[pH]]）&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;*:&amp;lt;math&amp;gt;\mathrm{pH} =-\log_{10} \frac{[\mathrm{H}^+]}{\mathrm{mol/L}}&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;*:&amp;lt;math&amp;gt;\mathrm{pH} =-\log_{10} \frac{[\mathrm{H}^+]}{\mathrm{mol/L}}&amp;lt;/math&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br/&gt;&lt;/td&gt;&lt;/tr&gt;

&lt;!-- diff cache key medicalware-mw_:diff::1.12:old-5291:rev-5292 --&gt;
&lt;/table&gt;</summary>
		<author><name>imported&gt;Mono Book</name></author>
	</entry>
	<entry>
		<id>https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5291&amp;oldid=prev</id>
		<title>imported&gt;Mono Book: ページの作成:「常用対数のグラフ &#039;&#039;&#039;常用対数&#039;&#039;&#039;（じょうようたいすう、common logarithm）とは、「10」...」</title>
		<link rel="alternate" type="text/html" href="https://medicalware.org/w/index.php?title=%E5%B8%B8%E7%94%A8%E5%AF%BE%E6%95%B0&amp;diff=5291&amp;oldid=prev"/>
		<updated>2014-10-29T10:06:44Z</updated>

		<summary type="html">&lt;p&gt;ページの作成:「&lt;a href=&quot;/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:Graph_of_common_logarithm.png&quot; title=&quot;ファイル:Graph of common logarithm.png&quot;&gt;thumb|350px|right|常用対数のグラフ&lt;/a&gt; &amp;#039;&amp;#039;&amp;#039;常用対数&amp;#039;&amp;#039;&amp;#039;（じょうようたいすう、common logarithm）とは、「10」...」&lt;/p&gt;
&lt;p&gt;&lt;b&gt;新規ページ&lt;/b&gt;&lt;/p&gt;&lt;div&gt;[[Image:Graph of common logarithm.png|thumb|350px|right|常用対数のグラフ]]&lt;br /&gt;
&amp;#039;&amp;#039;&amp;#039;常用対数&amp;#039;&amp;#039;&amp;#039;（じょうようたいすう、common logarithm）とは、「10」 を底とする[[対数]]である。&lt;br /&gt;
&lt;br /&gt;
== 定義と概要 ==&lt;br /&gt;
超大雑把に言えば「ある数字」と「省略された桁数（ゼロの数）」である。&lt;br /&gt;
&lt;br /&gt;
任意の正の数 &amp;#039;&amp;#039;x&amp;#039;&amp;#039; に対し、その常用対数 &amp;#039;&amp;#039;a&amp;#039;&amp;#039; は 10 を底とする対数として次の関係によって定められる（用語などの仔細はおおもとの[[対数]]の項を参照されたい）。&lt;br /&gt;
: &amp;#039;&amp;#039;a&amp;#039;&amp;#039; = log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; &amp;amp;hArr; 10&amp;lt;sup&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sup&amp;gt; = &amp;#039;&amp;#039;x&amp;#039;&amp;#039;&lt;br /&gt;
&lt;br /&gt;
例えば、log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; 2 ≒ 0.3010, log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; 3 ≒ 0.4771, log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; 100 = 2, log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; 1,000 = 3 となる。log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt;200 ≒ 2.301 で、整数部分（2）を常用対数の[[指標]]または標数（characteristic）、小数点以下の部分（.301）を[[仮数]]（mantissa）と言う。&lt;br /&gt;
&lt;br /&gt;
このとき任意の正の数 &amp;#039;&amp;#039;x&amp;#039;&amp;#039; を真数と呼び、10 を底という。&lt;br /&gt;
&lt;br /&gt;
底である 10 はしばしば省略を受け、単に log &amp;#039;&amp;#039;x&amp;#039;&amp;#039; と書かれる。このような省略は文脈上誤解の無い場合に行われ、常用対数の場合それは、工学や天文学等の十進法に基づく[[指数表記|科学的記数法]]の用いられる文脈であると考えられる（常用対数以外の特殊な底に関する略記に関しては[[対数]]の項参照）。&lt;br /&gt;
&lt;br /&gt;
常用対数の値は、その真数が 10 のどの程度の冪と[[オーダー (物理学)|同等の規模]]の数値であるのかを示す指針である。実際、実数 &amp;#039;&amp;#039;a&amp;#039;&amp;#039; (1 &amp;amp;le; &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;lt; 10) と非負の整数 &amp;#039;&amp;#039;s&amp;#039;&amp;#039; に対し &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;times; 10&amp;lt;sup&amp;gt;&amp;#039;&amp;#039;s&amp;#039;&amp;#039;&amp;lt;/sup&amp;gt; と表される実数の整数部分は十進で &amp;#039;&amp;#039;s&amp;#039;&amp;#039; + 1 桁であり、逆に log &amp;#039;&amp;#039;x&amp;#039;&amp;#039; の整数部分 [log &amp;#039;&amp;#039;x&amp;#039;&amp;#039;] が &amp;#039;&amp;#039;s&amp;#039;&amp;#039; に等しい正の数は &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;times; 10&amp;lt;sup&amp;gt;&amp;#039;&amp;#039;s&amp;#039;&amp;#039;&amp;lt;/sup&amp;gt; (1 &amp;amp;le; &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;lt; 10) の形に表される。さらに、実数 &amp;#039;&amp;#039;a&amp;#039;&amp;#039; (1 &amp;amp;le; &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;lt; 10) と負の整数 &amp;#039;&amp;#039;s&amp;#039;&amp;#039; に対し &amp;#039;&amp;#039;a&amp;#039;&amp;#039; &amp;amp;times; 10&amp;lt;sup&amp;gt;&amp;#039;&amp;#039;s&amp;#039;&amp;#039;&amp;lt;/sup&amp;gt; と表される数は、十進小数で小数首位（小数点以下に 0 でない数が現れる最初の桁）が小数第 (-&amp;#039;&amp;#039;s&amp;#039;&amp;#039;) 位となる。&lt;br /&gt;
&lt;br /&gt;
底の変換公式  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;a&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039;)  (log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;a&amp;#039;&amp;#039;) = log&amp;lt;sub&amp;gt;&amp;#039;&amp;#039;b&amp;#039;&amp;#039;&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;x&amp;#039;&amp;#039; によれば、常用対数の値は同じ数を真数とする[[自然対数]]の log&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; &amp;#039;&amp;#039;e&amp;#039;&amp;#039; = 約 0.43 倍の値を示す。&lt;br /&gt;
&lt;br /&gt;
*[[水素イオン指数]]&lt;br /&gt;
*:&amp;lt;math&amp;gt;\mathrm{pH} =-\log_{10} \frac{[\mathrm{H}^+]}{\mathrm{mol/L}}&amp;lt;/math&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== 常用対数表 ==&lt;br /&gt;
表の左は真数の小数点第1位までを、表の上は小数点第2位を示している。&lt;br /&gt;
つまり、左上から順に、真数が1.00,1.01,1.02のときの対数が書かれている。&lt;br /&gt;
それぞれの対数は、0.0000,0.0043,0.0086となる。&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
数   0     1     2     3     4     5     6     7     8     9&lt;br /&gt;
1.0 .0000 .0043 .0086 .0128 .0170 .0212 .0253 .0294 .0334 .0374&lt;br /&gt;
1.1 .0414 .0453 .0492 .0531 .0569 .0607 .0645 .0682 .0719 .0755&lt;br /&gt;
1.2 .0792 .0828 .0864 .0899 .0934 .0969 .1004 .1038 .1072 .1106&lt;br /&gt;
1.3 .1139 .1173 .1206 .1239 .1271 .1303 .1335 .1367 .1399 .1430&lt;br /&gt;
1.4 .1461 .1492 .1523 .1553 .1584 .1614 .1644 .1673 .1703 .1732&lt;br /&gt;
1.5 .1761 .1790 .1818 .1847 .1875 .1903 .1931 .1959 .1987 .2014&lt;br /&gt;
1.6 .2041 .2068 .2095 .2122 .2148 .2175 .2201 .2227 .2253 .2279&lt;br /&gt;
1.7 .2304 .2330 .2355 .2380 .2405 .2430 .2455 .2480 .2504 .2529&lt;br /&gt;
1.8 .2553 .2577 .2601 .2625 .2648 .2672 .2695 .2718 .2742 .2765&lt;br /&gt;
1.9 .2788 .2810 .2833 .2856 .2878 .2900 .2923 .2945 .2967 .2989&lt;br /&gt;
2.0 .3010 .3032 .3054 .3075 .3096 .3118 .3139 .3160 .3181 .3201&lt;br /&gt;
2.1 .3222 .3243 .3263 .3284 .3304 .3324 .3345 .3365 .3385 .3404&lt;br /&gt;
2.2 .3424 .3444 .3464 .3483 .3502 .3522 .3541 .3560 .3579 .3598&lt;br /&gt;
2.3 .3617 .3636 .3655 .3674 .3692 .3711 .3729 .3747 .3766 .3784&lt;br /&gt;
2.4 .3802 .3820 .3838 .3856 .3874 .3892 .3909 .3927 .3945 .3962&lt;br /&gt;
2.5 .3979 .3997 .4014 .4031 .4048 .4065 .4082 .4099 .4116 .4133&lt;br /&gt;
2.6 .4150 .4166 .4183 .4200 .4216 .4232 .4249 .4265 .4281 .4298&lt;br /&gt;
2.7 .4314 .4330 .4346 .4362 .4378 .4393 .4409 .4425 .4440 .4456&lt;br /&gt;
2.8 .4472 .4487 .4502 .4518 .4533 .4548 .4564 .4579 .4594 .4609&lt;br /&gt;
2.9 .4624 .4639 .4654 .4669 .4683 .4698 .4713 .4728 .4742 .4757&lt;br /&gt;
3.0 .4771 .4786 .4800 .4814 .4829 .4843 .4857 .4871 .4886 .4900&lt;br /&gt;
3.1 .4914 .4928 .4942 .4955 .4969 .4983 .4997 .5011 .5024 .5038&lt;br /&gt;
3.2 .5051 .5065 .5079 .5092 .5105 .5119 .5132 .5145 .5159 .5172&lt;br /&gt;
3.3 .5185 .5198 .5211 .5224 .5237 .5250 .5263 .5276 .5289 .5302&lt;br /&gt;
3.4 .5315 .5328 .5340 .5353 .5366 .5378 .5391 .5403 .5416 .5428&lt;br /&gt;
3.5 .5441 .5453 .5465 .5478 .5490 .5502 .5514 .5527 .5539 .5551&lt;br /&gt;
3.6 .5563 .5575 .5587 .5599 .5611 .5623 .5635 .5647 .5658 .5670&lt;br /&gt;
3.7 .5682 .5694 .5705 .5717 .5729 .5740 .5752 .5763 .5775 .5786&lt;br /&gt;
3.8 .5798 .5809 .5821 .5832 .5843 .5855 .5866 .5877 .5888 .5899&lt;br /&gt;
3.9 .5911 .5922 .5933 .5944 .5955 .5966 .5977 .5988 .5999 .6010&lt;br /&gt;
4.0 .6021 .6031 .6042 .6053 .6064 .6075 .6085 .6096 .6107 .6117&lt;br /&gt;
4.1 .6128 .6138 .6149 .6160 .6170 .6180 .6191 .6201 .6212 .6222&lt;br /&gt;
4.2 .6232 .6243 .6253 .6263 .6274 .6284 .6294 .6304 .6314 .6325&lt;br /&gt;
4.3 .6335 .6345 .6355 .6365 .6375 .6385 .6395 .6405 .6415 .6425&lt;br /&gt;
4.4 .6435 .6444 .6454 .6464 .6474 .6484 .6493 .6503 .6513 .6522&lt;br /&gt;
4.5 .6532 .6542 .6551 .6561 .6571 .6580 .6590 .6599 .6609 .6618&lt;br /&gt;
4.6 .6628 .6637 .6646 .6656 .6665 .6675 .6684 .6693 .6702 .6712&lt;br /&gt;
4.7 .6721 .6730 .6739 .6749 .6758 .6767 .6776 .6785 .6794 .6803&lt;br /&gt;
4.8 .6812 .6821 .6830 .6839 .6848 .6857 .6866 .6875 .6884 .6893&lt;br /&gt;
4.9 .6902 .6911 .6920 .6928 .6937 .6946 .6955 .6964 .6972 .6981&lt;br /&gt;
5.0 .6990 .6998 .7007 .7016 .7024 .7033 .7042 .7050 .7059 .7067&lt;br /&gt;
5.1 .7076 .7084 .7093 .7101 .7110 .7118 .7126 .7135 .7143 .7152&lt;br /&gt;
5.2 .7160 .7168 .7177 .7185 .7193 .7202 .7210 .7218 .7226 .7235&lt;br /&gt;
5.3 .7243 .7251 .7259 .7267 .7275 .7284 .7292 .7300 .7308 .7316&lt;br /&gt;
5.4 .7324 .7332 .7340 .7348 .7356 .7364 .7372 .7380 .7388 .7396&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
5.5 .7404 .7412 .7419 .7427 .7435 .7443 .7451 .7459 .7466 .7474&lt;br /&gt;
5.6 .7482 .7490 .7497 .7505 .7513 .7520 .7528 .7536 .7543 .7551&lt;br /&gt;
5.7 .7559 .7566 .7574 .7582 .7589 .7597 .7604 .7612 .7619 .7627&lt;br /&gt;
5.8 .7634 .7642 .7649 .7657 .7664 .7672 .7679 .7686 .7694 .7701&lt;br /&gt;
5.9 .7709 .7716 .7723 .7731 .7738 .7745 .7752 .7760 .7767 .7774&lt;br /&gt;
6.0 .7782 .7789 .7796 .7803 .7810 .7818 .7825 .7832 .7839 .7846&lt;br /&gt;
6.1 .7853 .7860 .7868 .7875 .7882 .7889 .7896 .7903 .7910 .7917&lt;br /&gt;
6.2 .7924 .7931 .7938 .7945 .7952 .7959 .7966 .7973 .7980 .7987&lt;br /&gt;
6.3 .7993 .8000 .8007 .8014 .8021 .8028 .8035 .8041 .8048 .8055&lt;br /&gt;
6.4 .8062 .8069 .8075 .8082 .8089 .8096 .8102 .8109 .8116 .8122&lt;br /&gt;
6.5 .8129 .8136 .8142 .8149 .8156 .8162 .8169 .8176 .8182 .8189&lt;br /&gt;
6.6 .8195 .8202 .8209 .8215 .8222 .8228 .8235 .8241 .8248 .8254&lt;br /&gt;
6.7 .8261 .8267 .8274 .8280 .8287 .8293 .8299 .8306 .8312 .8319&lt;br /&gt;
6.8 .8325 .8331 .8338 .8344 .8351 .8357 .8363 .8370 .8376 .8382&lt;br /&gt;
6.9 .8388 .8395 .8401 .8407 .8414 .8420 .8426 .8432 .8439 .8445&lt;br /&gt;
7.0 .8451 .8457 .8463 .8470 .8476 .8482 .8488 .8494 .8500 .8506&lt;br /&gt;
7.1 .8513 .8519 .8525 .8531 .8537 .8543 .8549 .8555 .8561 .8567&lt;br /&gt;
7.2 .8573 .8579 .8585 .8591 .8597 .8603 .8609 .8615 .8621 .8627&lt;br /&gt;
7.3 .8633 .8639 .8645 .8651 .8657 .8663 .8669 .8675 .8681 .8686&lt;br /&gt;
7.4 .8692 .8698 .8704 .8710 .8716 .8722 .8727 .8733 .8739 .8745&lt;br /&gt;
7.5 .8751 .8756 .8762 .8768 .8774 .8779 .8785 .8791 .8797 .8802&lt;br /&gt;
7.6 .8808 .8814 .8820 .8825 .8831 .8837 .8842 .8848 .8854 .8859&lt;br /&gt;
7.7 .8865 .8871 .8876 .8882 .8887 .8893 .8899 .8904 .8910 .8915&lt;br /&gt;
7.8 .8921 .8927 .8932 .8938 .8943 .8949 .8954 .8960 .8965 .8971&lt;br /&gt;
7.9 .8976 .8982 .8987 .8993 .8998 .9004 .9009 .9015 .9020 .9025&lt;br /&gt;
8.0 .9031 .9036 .9042 .9047 .9053 .9058 .9063 .9069 .9074 .9079&lt;br /&gt;
8.1 .9085 .9090 .9096 .9101 .9106 .9112 .9117 .9122 .9128 .9133&lt;br /&gt;
8.2 .9138 .9143 .9149 .9154 .9159 .9165 .9170 .9175 .9180 .9186&lt;br /&gt;
8.3 .9191 .9196 .9201 .9206 .9212 .9217 .9222 .9227 .9232 .9238&lt;br /&gt;
8.4 .9243 .9248 .9253 .9258 .9263 .9269 .9274 .9279 .9284 .9289&lt;br /&gt;
8.5 .9294 .9299 .9304 .9309 .9315 .9320 .9325 .9330 .9335 .9340&lt;br /&gt;
8.6 .9345 .9350 .9355 .9360 .9365 .9370 .9375 .9380 .9385 .9390&lt;br /&gt;
8.7 .9395 .9400 .9405 .9410 .9415 .9420 .9425 .9430 .9435 .9440&lt;br /&gt;
8.8 .9445 .9450 .9455 .9460 .9465 .9469 .9474 .9479 .9484 .9489&lt;br /&gt;
8.9 .9494 .9499 .9504 .9509 .9513 .9518 .9523 .9528 .9533 .9538&lt;br /&gt;
9.0 .9542 .9547 .9552 .9557 .9562 .9566 .9571 .9576 .9581 .9586&lt;br /&gt;
9.1 .9590 .9595 .9600 .9605 .9609 .9614 .9619 .9624 .9628 .9633&lt;br /&gt;
9.2 .9638 .9643 .9647 .9652 .9657 .9661 .9666 .9671 .9675 .9680&lt;br /&gt;
9.3 .9685 .9689 .9694 .9699 .9703 .9708 .9713 .9717 .9722 .9727&lt;br /&gt;
9.4 .9731 .9736 .9741 .9745 .9750 .9754 .9759 .9763 .9768 .9773&lt;br /&gt;
9.5 .9777 .9782 .9786 .9791 .9795 .9800 .9805 .9809 .9814 .9818&lt;br /&gt;
9.6 .9823 .9827 .9832 .9836 .9841 .9845 .9850 .9854 .9859 .9863&lt;br /&gt;
9.7 .9868 .9872 .9877 .9881 .9886 .9890 .9894 .9899 .9903 .9908&lt;br /&gt;
9.8 .9912 .9917 .9921 .9926 .9930 .9934 .9939 .9943 .9948 .9952&lt;br /&gt;
9.9 .9956 .9961 .9965 .9969 .9974 .9978 .9983 .9987 .9991 .9996&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== 関連項目 ==&lt;br /&gt;
* [[対数]]&lt;br /&gt;
* [[自然対数]]&lt;br /&gt;
* [[二進対数]]&lt;br /&gt;
* [[片対数グラフ]]&lt;br /&gt;
&lt;br /&gt;
==参考文献==&lt;br /&gt;
{{reflist}}&lt;br /&gt;
&lt;br /&gt;
{{stub}}&lt;br /&gt;
&lt;br /&gt;
{{DEFAULTSORT:しようようたいすう}}&lt;br /&gt;
[[Category:初等数学]]&lt;br /&gt;
[[Category:初等関数]]&lt;br /&gt;
[[Category:数学に関する記事]]&lt;/div&gt;</summary>
		<author><name>imported&gt;Mono Book</name></author>
	</entry>
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