Standard C++ Library User Guide and Tutorial

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Example Program - Roots of a Polynomial

Obtaining the Sample Program

The roots of a polynomial a x2 + b x + c = 0 are given by the formula:

x = (-b _ sqrt(b2 - 4ac))/2a

The following program takes as input three double precision numbers, and returns the complex

roots as a pair of values.

typedef complex<double> dcomplex;

pair<dcomplex, dcomplex> quadratic

(dcomplex a, dcomplex b, dcomplex c)

// return the roots of a quadratic equation

{

dcomplex root = sqrt(b * b - 4.0 * a * c);

a *= 2.0;

return make_pair(

(-b + root)/a,

(-b - root)/a);

}