# __cospi(3) [mojave man page]

__COSPI(3) BSD Library Functions Manual __COSPI(3)NAME

__cospicosine-pi function--SYNOPSIS

#include <math.h> float __cospif(float x); double __cospi(double x);DESCRIPTION

The __cospi() function returns the cosine of pi times x (measured in radians). This can be computed more accurately than cos(M_PI * x), because it can implicitly use as many bits of pi as are necessary to deliver a well-rounded result, instead of the 53-bits to which M_PI is limited. For large x it may also be more efficient, as the argument reduction involved is significantly simpler. This function may be especially useful for working with degrees; whereas cos(M_PI * x / 180.0) cannot produce exact results for angles that naively "should" be exact, like 90 degrees, __cospi(x / 180.0) can be computed exactly.SPECIAL VALUES

__cospi(-x) is the same as __cospi(x) for any finite x. __cospi(n) returns +1 for any even integer n. __cospi(n) returnsfor any odd integer n. __cospi(n + 0.5) returns +0 for any integer n. __cospi(+-infinity) raises the invalid floating-point exception and returns NaN.-1VECTOR OPERATIONS

If you need to apply the __cospi() function to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may be useful: #include <Accelerate/Accelerate.h> vFloat vcospif(vFloat x); void vvcospif(float *y, const float *x, const int *n); void vvcospi(double *y, const double *x, const int *n);SEE ALSO

__sinpi(3), __tanpi(3), __sincospi(3), math(3)BSD

December 15, 2012 BSD

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NAME

__cospicosine-pi function--SYNOPSIS

#include <math.h> float __cospif(float x); double __cospi(double x);DESCRIPTION

The __cospi() function returns the cosine of pi times x (measured in radians). This can be computed more accurately than cos(M_PI * x), because it can implicitly use as many bits of pi as are necessary to deliver a well-rounded result, instead of the 53-bits to which M_PI is limited. For large x it may also be more efficient, as the argument reduction involved is significantly simpler. This function may be especially useful for working with degrees; whereas cos(M_PI * x / 180.0) cannot produce exact results for angles that naively "should" be exact, like 90 degrees, __cospi(x / 180.0) can be computed exactly.SPECIAL VALUES

__cospi(-x) is the same as __cospi(x) for any finite x. __cospi(n) returns +1 for any even integer n. __cospi(n) returnsfor any odd integer n. __cospi(n + 0.5) returns +0 for any integer n. __cospi(+-infinity) raises the invalid floating-point exception and returns NaN.-1VECTOR OPERATIONS

If you need to apply the __cospi() function to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may be useful: #include <Accelerate/Accelerate.h> vFloat vcospif(vFloat x); void vvcospif(float *y, const float *x, const int *n); void vvcospi(double *y, const double *x, const int *n);SEE ALSO

__sinpi(3), __tanpi(3), __sincospi(3), math(3)BSD

December 15, 2012 BSD