📄 11.htm
字号:
<html>
<head>
<title>符号表达式</title>
</head>
<body lang=ZH-CN link=blue vlink=purple style='tab-interval:21.0pt;text-justify-trim:
punctuation'>
<div class=Section1 style='layout-grid:15.6pt'>
<p class=MsoNormal align=center style='text-align:center'><b><span
style='font-size:26.0pt;mso-bidi-font-size:12.0pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>符号计算</span></b><span
lang=EN-US style='font-size:12.0pt;font-family:宋体;mso-font-kerning:0pt'><o:p></o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-font-kerning:0pt'>
<hr size=2 width="100%" align=center>
</span></div>
<p class=MsoNormal align=center style='text-align:center'><b><span
style='font-size:16.0pt;mso-bidi-font-size:12.0pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>符号表达式</span></b><b><span
lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;color:blue'><o:p></o:p></span></b></p>
<p class=MsoNormal align=center style='text-align:center'><span lang=EN-US
style='font-size:12.0pt;font-family:宋体;mso-font-kerning:0pt'> <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:2.0gd'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>在</span><span
lang=EN-US>MATLAB</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>中是将一符号表示式储存唯一字串</span> <span
lang=EN-US>(character string)</span><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>，即是以二个单引号之内的表示式来定义其为</span>
<span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>一符号式，例如</span> <span lang=EN-US style='color:red'>'tan(x)'</span><span
lang=EN-US>,<span style='color:red'> 'x^4 +2*x^2 /5'</span> </span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>的两个式子。</span></p>
<p class=MsoNormal style='margin-left:42.0pt;text-indent:-21.0pt;mso-list:l1 level1 lfo1;
tab-stops:list 42.0pt'><span class=Input><span lang=EN-US
style='mso-ansi-font-size:10.5pt;font-family:Wingdings;color:windowtext;
font-weight:normal'>l<span style='font:7.0pt "Times New Roman"'>
</span></span></span> <span class=Input><span style='font-size:10.0pt;
mso-bidi-font-size:12.0pt;font-family:宋体;mso-ascii-font-family:"Courier New";
mso-hansi-font-family:"Courier New";color:windowtext;font-weight:normal'>把字符表达式转换为符号变量</span></span><span
class=Input><span lang=EN-US style='mso-ansi-font-size:10.5pt;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:windowtext;
font-weight:normal'><o:p></o:p></span></span></p>
<p class=MsoNormal style='margin-left:2.0gd;tab-stops:21.25pt;mso-layout-grid-align:
none;punctuation-wrap:simple'><span class=Input><span lang=EN-US
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:"Courier New";
mso-bidi-font-family:"Times New Roman";color:blue;font-weight:normal'>y=sym('2*sin(x)*cos(x)')<span
style='mso-tab-count:1'> </span>%</span></span><span class=Input><span
style='font-size:10.0pt;mso-bidi-font-size:12.0pt;font-family:宋体;mso-ascii-font-family:
"Courier New";mso-hansi-font-family:"Courier New";color:blue;font-weight:normal'>把字符表达式转换为符号变量</span></span><span
class=Input><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:12.0pt;
font-family:"Courier New";mso-bidi-font-family:"Times New Roman";color:blue;
font-weight:normal'><o:p></o:p></span></span></p>
<p class=Normal style='margin-left:2.0gd'><span class=Input><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";mso-bidi-font-family:"Times New Roman";
color:blue;font-weight:normal'>y=simple(y) <span style='mso-tab-count:6'> </span>%</span></span><span
class=Input><span style='font-size:10.0pt;font-family:宋体;mso-ascii-font-family:
"Courier New";mso-hansi-font-family:"Courier New";color:blue;font-weight:normal'>按规则把已有的</span></span><span
class=Input><span lang=EN-US style='font-size:10.0pt;font-family:"Courier New";
mso-bidi-font-family:"Times New Roman";color:blue;font-weight:normal'>y</span></span><span
class=Input><span style='font-size:10.0pt;font-family:宋体;mso-ascii-font-family:
"Courier New";mso-hansi-font-family:"Courier New";color:blue;font-weight:normal'>符号表达式化成最简形式</span></span><b><span
style='color:blue'> <span lang=EN-US><o:p></o:p></span></span></b></p>
<p class=Normal style='margin-left:2.0gd'><span class=Output><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";mso-bidi-font-family:"Times New Roman"'>y
=<o:p></o:p></span></span></p>
<p class=Normal style='margin-left:2.0gd'><span class=Output><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";mso-bidi-font-family:"Times New Roman"'>2*sin(x)*cos(x)<o:p></o:p></span></span></p>
<p class=Normal style='margin-left:2.0gd'><span class=Output><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";mso-bidi-font-family:"Times New Roman"'>y
=<o:p></o:p></span></span></p>
<p class=Normal style='margin-left:2.0gd'><span class=Output><span lang=EN-US
style='font-size:10.0pt;font-family:"Courier New";mso-bidi-font-family:"Times New Roman"'>sin(2*x)
</span></span><span lang=EN-US style='color:blue'><span style="mso-spacerun:
yes"> </span><o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>
<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>
<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>
<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>?syms
x%</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman";color:blue'>这个必须先定义一个变量</span><span
lang=EN-US style='color:blue'>X<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>?A=[3/2,(x^2+3)/(2*x-1)+3*x/(x-1);4/x^2,3*x+4]<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'><span
style="mso-spacerun: yes"> </span><o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>A
=<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'><span
style="mso-spacerun: yes"> </span><o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>[<span
style="mso-spacerun:
yes">
</span>3/2, (x^2+3)/(2*x-1)+3*x/(x-1)]<o:p></o:p></span></p>
<p class=Normal style='margin-left:2.0gd'><span lang=EN-US style='color:blue'>[<span
style="mso-spacerun:
yes">
</span>4/x^2,<span style="mso-spacerun:
yes">
</span>3*x+4]<o:p></o:p></span></p>
<p class=Normal><span lang=EN-US> <o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:42.0pt;text-indent:-21.0pt;mso-list:l1 level1 lfo1;
tab-stops:list 42.0pt'><span lang=EN-US style='font-family:
Wingdings'>l<span style='font:7.0pt "Times New Roman"'>
</span></span> <span lang=EN-US>MATLAB</span><span style='font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>提供了一个函数</span><span
lang=EN-US style='color:red'>ezplot</span><span lang=EN-US> </span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>可以画单变数的符号式</span></p>
<p class=MsoNormal align=center style='margin-left:21.0pt;text-align:center'><b><span
style='font-size:16.0pt;mso-bidi-font-size:12.0pt;font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";color:blue'>符号函数</span></b><b><span
lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;color:blue'><o:p></o:p></span></b></p>
<table border=1 cellspacing=0 cellpadding=0 style='border-collapse:collapse;
border:none;mso-border-alt:solid windowtext .5pt;mso-padding-alt:0cm 5.4pt 0cm 5.4pt'>
<tr>
<td width=239 valign=top style='width:179.6pt;border:solid windowtext .5pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'><span lang=EN-US style='font-family:
"Times New Roman";color:red'>horner(S)<o:p></o:p></span></p>
</td>
<td width=329 valign=top style='width:246.5pt;border:solid windowtext .5pt;
border-left:none;mso-border-left-alt:solid windowtext .5pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'>将<span lang=EN-US style='font-family:
"Times New Roman"'>S</span>转换成巢状表示式<span lang=EN-US style='font-family:"Times New Roman"'><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=239 valign=top style='width:179.6pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'><span lang=EN-US style='font-family:
"Times New Roman";color:red'>numden(S)<o:p></o:p></span></p>
</td>
<td width=329 valign=top style='width:246.5pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'>将<span lang=EN-US style='font-family:
"Times New Roman"'>S</span>的有理数表示成分子和分母的形式<span lang=EN-US style='font-family:
"Times New Roman"'><o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=239 valign=top style='width:179.6pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'><span lang=EN-US style='font-family:
"Times New Roman";color:red'>numeric(S)<o:p></o:p></span></p>
</td>
<td width=329 valign=top style='width:246.5pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'>将<span lang=EN-US style='font-family:
"Times New Roman"'>S</span>改成数值式<span lang=EN-US style='font-family:"Times New Roman"'>(S</span>不能含有任何符号变数<span
lang=EN-US style='font-family:"Times New Roman"'>)<o:p></o:p></span></p>
</td>
</tr>
<tr>
<td width=239 valign=top style='width:179.6pt;border:solid windowtext .5pt;
border-top:none;mso-border-top-alt:solid windowtext .5pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'><span lang=EN-US style='font-family:
"Times New Roman";color:red'>poly2sym(c)<o:p></o:p></span></p>
</td>
<td width=329 valign=top style='width:246.5pt;border-top:none;border-left:
none;border-bottom:solid windowtext .5pt;border-right:solid windowtext .5pt;
mso-border-top-alt:solid windowtext .5pt;mso-border-left-alt:solid windowtext .5pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p align=center style='text-align:center'>转换多项式系数向量<span lang=EN-US
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