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| <TITLE>Example Program: Roots of a Polynomial</TITLE> |
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| <H2>20.3 Example Program: Roots of a Polynomial</H2> |
| <A NAME="idx445"><!></A> |
| <BLOCKQUOTE><HR><B> |
| NOTE -- This program is in the file complx.cpp. |
| </B><HR></BLOCKQUOTE> |
| <P>The roots of a polynomial <IMG SRC="images/stdlibug-SpecialClassesa.gif" WIDTH=128 HEIGHT=29>are given by the formula:</P> |
| <P><IMG SRC="images/stdlibug-SpecialClasses2.gif" WIDTH=177 HEIGHT=71></P> |
| <P>The following function takes as input three double precision numbers, and returns the complex roots as a pair of values.</P> |
| |
| <UL><PRE> |
| typedef std::complex<double> dcomplex; |
| |
| std::pair<dcomplex, dcomplex> quadratic |
| (dcomplex a, dcomplex b, dcomplex c) |
| // return the roots of a quadratic equation |
| { |
| dcomplex root = std::sqrt(b * b - 4.0 * a * c); |
| a *= 2.0; |
| return std::make_pair( (-b + root)/a, |
| (-b - root)/a ); |
| } |
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