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<! Made by Html Translation Ver 1.0><html><head><title> 积分 </title></head><body BACKGROUND="../img1/bg0000.gif" tppabs="http://webclass.ncu.edu.tw/~junwu/img/bg0000.gif"><script language="JAVASCRIPT"><!--if (navigator.onLine){document.write("<!-- Spidersoft WebZIP Ad Banner Insert -->");document.write("<TABLE width=100% border=0 cellpadding=0 cellspacing=0>");document.write("<TR>");document.write("<TD>");document.write("<ILAYER id=ad1 visibility=hidden height=60></ILAYER>");document.write("<NOLAYER>");document.write("<IFRAME SRC='http://www.spidersoft.com/ads/bwz468_60.htm' width=100% height=60 marginwidth=0 marginheight=0 hspace=0 vspace=0 frameborder=0 scrolling=no></IFRAME>");document.write("</NOLAYER>");document.write("</TD>");document.write("</TR>");document.write("</TABLE>");document.write("<!-- End of Spidersoft WebZIP Ad Banner Insert-->");} //--></script><!-- Spidersoft WebZIP Ad Banner Insert --><!-- End of Spidersoft WebZIP Ad Banner Insert--><font COLOR="#0000FF"><h1>11.3.2 积分</h1></font><hr><p><font COLOR="#FF0000" FACE="Times New Roman">int</font>函数用以演算一函数的积分项， 这个函数要找出一符号式<font COLOR="#FF0000"> </font><font COLOR="#FF0000" FACE="Times New Roman">F </font>使得<font COLOR="#FF0000" FACE="Times New Roman">diff(F)=f</font>。如果积分式的解析式 <font FACE="Times New Roman">(analytical form, closed form) </font>不存在的话或是MATLAB无法找到，则<font COLOR="#FF0000"> </font><font COLOR="#FF0000" FACE="Times New Roman">int </font>传回原输入的符号式。相关的函数语法有下列 4个： </p><p><font COLOR="#FF0000" FACE="Times New Roman">int(f)</font> 传回<font COLOR="#FF0000" FACE="Times New Roman">f</font>对预设独立变数的积分值 </p><p><font COLOR="#FF0000" FACE="Times New Roman">int(f,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">t</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">)</font> 传回<font COLOR="#FF0000" FACE="Times New Roman">f</font>对独立变数<font COLOR="#FF0000" FACE="Times New Roman">t</font>的积分值 </p><p><font COLOR="#FF0000" FACE="Times New Roman">int(f,a,b)</font> 传回<font COLOR="#FF0000" FACE="Times New Roman">f</font>对预设独立变数的积分值，积分区间为<font COLOR="#FF0000" FACE="Times New Roman">[a,b]</font>，<font COLOR="#FF0000" FACE="Times New Roman">a</font>和<font COLOR="#FF0000" FACE="Times New Roman">b</font>为数值式 </p><p><font COLOR="#FF0000" FACE="Times New Roman">int(f,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">t</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">,a,b)</font> 传回<font COLOR="#FF0000" FACE="Times New Roman">f</font>对独立变数<font COLOR="#FF0000" FACE="Times New Roman">t</font>的积分值，积分区间为<font COLOR="#FF0000" FACE="Times New Roman">[a,b]</font>，<font COLOR="#FF0000" FACE="Times New Roman">a</font>和<font COLOR="#FF0000" FACE="Times New Roman">b</font>为数值式 </p><p><font COLOR="#FF0000" FACE="Times New Roman">int(f,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">m</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">n</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">)</font> 传回<font COLOR="#FF0000" FACE="Times New Roman">f</font>对预设变数的积分值，积分区间为<font COLOR="#FF0000" FACE="Times New Roman">[m,n]</font>，<font COLOR="#FF0000" FACE="Times New Roman">m</font>和<font COLOR="#FF0000" FACE="Times New Roman">n</font>为符号式 <br></p><p>我们示范几个例子： </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>S1 = </font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">6*x^3-4*x^2+b*x-5</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">;</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>S2 = </font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">sin(a)</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">;</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>S3 = </font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">sqrt(x)</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">; <br></font></p><p><font COLOR="#FF0000" FACE="Times New Roman">>>int(S1)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">3/2*x^4-4/3*x^3+1/2*b*x^2-5*x</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>int(S2)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">-cos(a)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>int(S3)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">2/3*x^(3/2)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>int(S3,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">a</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">,</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">b</font><font COLOR="#FF0000">'</font><font COLOR="#FF0000" FACE="Times New Roman">)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">2/3*b^(3/2)- 2/3*a^(3/2)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>int(S3,0.5,0.6)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">2/25*15^(1/2)-1/6*2^(1/2)</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">>>numeric(int(S3,0.5,0.6)) % </font>使用<font COLOR="#FF0000" FACE="Times New Roman">numeric</font>函数可以计算积分的数值 </p><p><font COLOR="#FF0000" FACE="Times New Roman">ans=</font> </p><p><font COLOR="#FF0000" FACE="Times New Roman">0.0741<br></font></p><hr><a HREF="ch11_3_1.htm" tppabs="http://webclass.ncu.edu.tw/~junwu/ch11_3_1.htm"><p><img SRC="../img1/lastpage.gif" tppabs="http://webclass.ncu.edu.tw/~junwu/img/lastpage.gif" BORDER="0" WIDTH="42" HEIGHT="42"></a> <a HREF="ch11_4.htm" tppabs="http://webclass.ncu.edu.tw/~junwu/ch11_4.htm"><img SRC="../img1/nextpage.gif" tppabs="http://webclass.ncu.edu.tw/~junwu/img/nextpage.gif" BORDER="0" HSPACE="10" WIDTH="42" HEIGHT="42"></a> <a HREF="../index.html" tppabs="http://webclass.ncu.edu.tw/~junwu/index.html"><img SRC="../img1/outline.gif" tppabs="http://webclass.ncu.edu.tw/~junwu/img/outline.gif" BORDER="0" HSPACE="6" WIDTH="42" HEIGHT="42"></a><br><font SIZE="2" COLOR="#AA55FF">上一页 下一页 讲义大纲 </font><layer src="http://www.spidersoft.com/ads/bwz468_60.htm" visibility="hidden" id="a1" width="600" onload="moveToAbsolute(ad1.pageX,ad1.pageY); 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