Manual Pages  — COSPI

cospi, cospif, cospil – half-cycle cosine functions

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES SPECIAL VALUES SEE ALSO AUTHORS STANDARDS

Math Library (libm, -lm)

#include <math.h>

double
cospi(double x);

float
cospif(float x);

long double
cospil(long double x);

The cospi(), cospif(), and cospil() functions compute the cosine of π µ x. and measure angles in half-cycles.

The cospi(), cospif(), and cospil() functions returns cos(π µ x). If |x| ≥ 2^(p - 1) where p is the floating-point precision of x, then the returned value is 1 and it has no significance.

	cospi(±0) returns 1.
	cospi(±n/2) returns 0 for positive integers n.
	cospi(n) returns 1 for even integers n.
	cospi(n) returns -1 for odd integers n.
	cospi(±∞) return an NaN and raises an FE_INVALID exception.
	cospi(NaN) return an NaN and raises an FE_INVALID exception.

The half-cycle trignometric functions were written by Steven G. Kargl <Mt kargl@FreeBSD.org>.

These functions conform to IEEE Std 754&#174;-2008 , dqIEEE Standard for Floating-Point Arithmeticdq and to ISO/IEC TS 18661-4 , dqInformation technology &#151; Programming languages, their environments, and system software interfaces &#151; Floating-point extensions for Cdq &#151; Part 4: Supplementary functions.