cos_pi

#include <boost/math/special_functions/cos_pi.hpp>

namespace boost{ namespace math{

template <class T>
calculated-result-type cos_pi(T x);

template <class T, class Policy>
calculated-result-type cos_pi(T x, const Policy&);

}} // namespaces

Returns the cosine of πx.

The return type of this function is computed using the result type calculation rules: the return is double when x is an integer type and T otherwise.

The final Policy argument is optional and can be used to control the behaviour of the function: how it handles errors, what level of precision to use etc. Refer to the policy documentation for more details.

This function performs exact all-integer arithmetic argument reduction before computing the cosine of πx.

Table 6.77. Error rates for cos_pi

	Microsoft Visual C++ version 12.0 Win32 double	GNU C++ version 5.1.0 linux double	GNU C++ version 5.1.0 linux long double	Sun compiler version 0x5130 Sun Solaris long double
sin_pi and cos_pi	Max = 0.996ε (Mean = 0.281ε)	Max = 0ε (Mean = 0ε)	Max = 0.991ε (Mean = 0.302ε)	Max = 0.991ε (Mean = 0.302ε)
sin_pi and cos_pi near integers and half integers	Max = 0.996ε (Mean = 0.298ε)	Max = 0ε (Mean = 0ε)	Max = 0.976ε (Mean = 0.28ε)	Max = 0.976ε (Mean = 0.28ε)