__TANPI(3) BSD Library Functions Manual __TANPI(3)NAME__tanpi — tangent-pi function
SYNOPSIS
#include <math.h>
float
__tanpif(float x);
double
__tanpi(double x);
DESCRIPTION
The __tanpi() function returns the tangent of pi times x (measured in
radians). This can be computed more accurately than tan(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
tan(M_PI * x / 180.0) cannot produce exact results for angles that
naively "should" be exact, like 90 degrees, __tanpi(x / 180.0) can be
computed exactly.
SPECIAL VALUES
__tanpi(-x) is the same as - __tanpi(x) for any finite x.
__tanpi(�0) returns �0.
__tanpi(n) returns +0 for any positive even integer n.
__tanpi(n) returns -0 for any positive odd integer n.
__tanpi(n + 0.5) returns +infinity for any even integer n.
__tanpi(n + 0.5) returns -infinity for any odd integer n.
__tanpi(�infinity) raises the invalid floating-point exception and
returns NaN.
VECTOR OPERATIONS
If you need to apply the __tanpi() function to SIMD vectors or arrays,
using the following functions provided by the Accelerate.framework may be
useful:
#include <Accelerate/Accelerate.h>
vFloat vtanpif(vFloat x);
void vvtanpif(float *y, float *x, const int n);
void vvtanpi(double *y, double *x, const int n);
SEE ALSO__cospi(3), __sinpi(3), __sincospi(3), math(3)BSD December 15, 2012 BSD
