#include <cmath>
    double cos( double arg );

The cos() function returns the cosine of arg, where arg is expressed in radians. The return value of cos() is in the range [-1,1]. If arg is infinite, cos() will return NAN and raise a floating-point exception.

C++ also provides the following overloaded forms:

    #include <cmath>
    float cos( float arg ); // same as cosf() in C99
    long double cos( long double arg ); // same as cosl() in C99

Related Topics: acos, asin, atan, atan2, cosh, sin, sinh, tan, tanh