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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.