Kernel Cosine

Compute the cosine of a number on [-π/4, π/4].

Usage

var kernelCos = require( '@stdlib/math/base/special/kernel-cos' );

kernelCos( x, y )

Computes the cosine of a number on [-π/4, π/4]. 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 x and y).

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

As components of a double-double number, the two double-precision floating-point numbers x and y must satisfy
where ulp stands 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 ) );
}