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 π × x. and measure angles in half-cycles.
RETURN VALUES
The cospi(), cospif(), and cospil() functions returns cos(π × 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(∞)
-
return an and raises an FE_INVALID exception.
- cospi()
-
return an 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 ⟨[email protected]⟩.
STANDARDS
These functions conform to IEEE Std 754-2008, 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, and to ISO/IEC 9899:2024 (“ISO C23”).