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<p style="line-height: 150%" align="center"><font size="4"><b><a name="content-1-1-2-lianjieci"></a>联
结 词</b></font></p>
<p style="line-height: 150%">在命题逻辑中有以下几种基本的联结词： </p>
<p style="line-height: 150%" align="center">
<img src="image/fei.gif" width="10" height="5" > <img src="image/hequ.gif" width="9" height="11" >
<img src="image/xiqu.gif" width="9" height="15" > <img src="image/yunhan.gif" width="15" height="9" >
<img src="image/dengtong.gif" width="16" height="9" ></p>
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<b>
1、<font color="#000000" >非、否定</font>(<img src="image/fei.gif" width="10" height="5">),</b><br>
定义：给定命题P，命题R当且仅当P为假时为真，则称R为P的否定或非P，记为：<img src="image/fei.gif" width="10" height="5" >P。<br>
其定义可用如下真值表表示:</p>
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<div align="center"> P</div>
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<div align="center"><img src="image/fei.gif" width="10" height="5">P</div>
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<td width="53%">
<div align="center">0</div>
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<td width="47%">
<div align="center">1</div>
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<td width="53%" height="23">
<div align="center">1</div>
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<td width="47%" height="23">
<div align="center">0</div>
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<p style="line-height: 150%" > <b> 例：</b>今天不下雨。<br>
设：P：今天下雨，则原命题为<img src="image/fei.gif" width="10" height="5" >P。</p>
<p style="line-height: 150%" ><b><a name="hequ"></a>2、合取(<img src="image/hequ.gif" width="9" height="11">),</b><br>
定义：给定两个命题P、Q，若命题R当且仅当P、Q同时为真时为真，则称R为P、Q的合取，记为：P<img src="image/hequ.gif" width="9" height="11">Q。<br>
其定义可用如下真值表表示:</p>
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<td width="30%" align="center">
<div align="center">P</div>
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<td width="30%" align="center">
<div align="center">Q</div>
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<td width="40%" align="center">
<div align="center">P<img src="image/hequ.gif" width="9" height="11">Q</div>
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<td width="30%" align="center">
<div align="center">0</div>
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0
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<td width="40%" align="center">
<div align="center">0</div>
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<td width="30%" align="center">
<div align="center">0</div>
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1
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<td width="40%" align="center">
<div align="center">0</div>
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<td width="30%" align="center">
<div align="center">1</div>
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<td width="30%" align="center">
<div align="center">0</div>
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<td width="40%" align="center">
<div align="center">0</div>
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<td width="30%" align="center">
<div align="center">1</div>
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1
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<td width="40%" align="center">
<div align="center">1</div>
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<p style="line-height: 150%" ><b> 例：</b>张三和李四都是三好学生。<br>
设：P：张三是三好学生；Q：李四是三好学生。<br>
则原命题为：P<img src="image/hequ.gif" width="9" height="11">Q</p>
<p style="line-height: 150%" > <b><font color="#FF0000">注：</font></b>并非所有的“和”都表示“合取”，例如，王五和赵六是兄弟。<br>
当谓词描述的是对象之间的关系时不能用合取。</p>
<p style="line-height: 150%" > </p>
<p style="line-height: 150%" ><b><a name="xiqu"></a>3、析取(<img src="image/xiqu.gif" width="9" height="15">),</b><br>
定义：给定两个命题P、Q，若命题R当且仅当P、Q中至少有一个为真时为真，则称R为P、Q的析取，记为：P<img src="image/xiqu.gif" width="9" height="15">Q。<br>
其定义可用如下真值表表示:</p>
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<table width="23%" border="1">
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<td width="30%">
<div align="center">P</div>
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<td width="30%">
<div align="center">Q</div>
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<td width="40%">
<div align="center">P<img src="image/xiqu.gif" width="9" height="15">Q</div>
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<td width="30%" align="center">
<div align="center">0</div>
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<td width="30%" align="center">
0
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<td width="40%" align="center">
<div align="center">0</div>
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