__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
Mac OS X 10.9.1 - Generated Fri Jan 10 06:10:10 CST 2014