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COSPI(3) FreeBSD Library Functions Manual COSPI(3)
NAME cospi, cospif, cospil - half-cycle cosine functions
LIBRARY Math Library (libm, -lm)
SYNOPSIS #include <math.h>
double cospi(double x);
float cospif(float x);
long double cospil(long double x);
DESCRIPTION The cospi(), cospif(), and cospil() functions compute the cosine of <pi> x x. and measure angles in half-cycles.
RETURN VALUES The cospi(), cospif(), and cospil() functions returns cos(<pi> x 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.
SPECIAL VALUES 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(+-<infinity>) return an NaN and raises an FE_INVALID exception.
cospi(NaN) return an NaN and raises an FE_INVALID exception.
SEE ALSO cos(3), fenv(3), math(3), sin(3), sinpi(3), tan(3), tanpi(3)
AUTHORS The half-cycle trignometric functions were written by Steven G. Kargl <kargl@FreeBSD.org>.
STANDARDS These functions conform to IEEE Std 754tm-2008 , "IEEE Standard for Floating-Point Arithmetic" and to ISO/IEC TS 18661-4 , "Information technology -- Programming languages, their environments, and system software interfaces -- Floating-point extensions for C" -- Part 4: Supplementary functions.