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__SINPI(3)               BSD Library Functions Manual               __SINPI(3)

NAME
     __sinpi -- sine-pi function

SYNOPSIS
     #include <math.h>

     float
     __sinpif(float x);

     double
     __sinpi(double x);

DESCRIPTION
     The __sinpi() function returns the sine of pi times x (measured in radians).  This can be computed more
     accurately than sin(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 sin(M_PI * x / 18_._) cannot
     produce exact results for angles that naively "should" be exact, like 180 degrees, __sinpi(x / 18_._)
     can be computed exactly.

SPECIAL VALUES
     __sinpi(-x) is the same as - __sinpi(x) for any finite x.
     __sinpi(+-_) returns +-0.
     __sinpi(n) returns +0 for any positive integer n.
     __sinpi(n + _.5) returns +1 for any even integer n.
     __sinpi(n + _.5) returns -1 for any odd integer n.
     __sinpi(+-infinity) raises the invalid floating-point exception and returns NaN.

VECTOR OPERATIONS
     If you need to apply the __sinpi() function to SIMD vectors or arrays, using the following functions
     provided by the Accelerate.framework may be useful:

     #include <Accelerate/Accelerate.h>

     vFloat vsinpif(vFloat x);
     void vvsinpif(float *y, float *x, const int n);
     void vvsinpi(double *y, double *x, const int n);

SEE ALSO
     __cospi(3), __tanpi(3), __sincospi(3), math(3)

BSD                            December 15, 2012                           BSD