kernelCos
Compute the cosine of a double-precision floating-point number on
[-π/4, π/4].
Usage
var kernelCos = require( '@stdlib/math/base/special/kernel-cos' );
kernelCos( x, y )
Computes the cosine of a double-precision floating-point number on [-π/4, π/4].
var v = kernelCos( 0.0, 0.0 );
// returns ~1.0
v = kernelCos( 3.141592653589793/6.0, 0.0 );
// returns ~0.866
v = kernelCos( 0.785, -1.144e-17 );
// returns ~0.707
v = kernelCos( NaN, 0.0 );
// returns NaN
Notes
For increased accuracy, the number for which the cosine should be evaluated can be supplied as a double-double number (i.e., a non-evaluated sum of two double-precision floating-point numbers
xandy).As components of a double-double number, the two double-precision floating-point numbers
xandymust satisfywhere
ulpstands for units in the last place.
Examples
var linspace = require( '@stdlib/array/base/linspace' );
var PI = require( '@stdlib/constants/float64/pi' );
var kernelCos = require( '@stdlib/math/base/special/kernel-cos' );
var x = linspace( -PI/4.0, PI/4.0, 100 );
var i;
for ( i = 0; i < x.length; i++ ) {
console.log( 'kernelCos(%d) = %d', x[ i ], kernelCos( x[ i ], 0.0 ) );
}
C APIs
Usage
#include "stdlib/math/base/special/kernel_cos.h"
stdlib_base_kernel_cos( x, y )
Computes the cosine of a double-precision floating-point number on [-π/4, π/4].
var v = stdlib_base_kernel_cos( 0.0, 0.0 );
// returns ~0.0
v = stdlib_base_kernel_cos( 3.141592653589793/6.0, 0.0 );
// returns ~0.866
The function accepts the following arguments:
- x:
[in] doubleinput value (in radians, assumed to be bounded by~pi/4in magnitude). - y:
[in] doubletail ofx.
double stdlib_base_kernel_cos( const double x, const double y );
Notes
- For increased accuracy, the number for which the cosine should be evaluated can be supplied as a double-double number (i.e., a non-evaluated sum of two double-precision floating-point numbers
xandy).
Examples
#include "stdlib/math/base/special/kernel_cos.h"
#include <stdio.h>
int main( void ) {
const double x[] = { -0.7853981633974483, -0.6108652381980153, -0.4363323129985824, -0.26179938779914946, -0.08726646259971649, 0.08726646259971649, 0.26179938779914935, 0.43633231299858233, 0.6108652381980153, 0.7853981633974483 };
double out;
int i;
for ( i = 0; i < 10; i++ ) {
out = stdlib_base_kernel_cos( x[ i ], 0.0 );
printf ( "x[ i ]: %lf, y: %lf, out: %lf\n", x[ i ], 0.0, out );
}
}