cospi

Compute the cosine of a number times π.

Usage

var cospi = require( '@stdlib/math/base/special/cospi' );

cospi( x )

Computes cos(πx) more accurately than cos(pi*x), especially for large x.

var y = cospi( 0.0 );
// returns 1.0

y = cospi( 0.5 );
// returns 0.0

y = cospi( 0.1 );
// returns ~0.951

y = cospi( NaN );
// returns NaN

Examples

var linspace = require( '@stdlib/array/base/linspace' );
var cospi = require( '@stdlib/math/base/special/cospi' );

var x = linspace( -100.0, 100.0, 100 );

var i;
for ( i = 0; i < x.length; i++ ) {
    console.log( cospi( x[ i ] ) );
}

C APIs

Usage

#include "stdlib/math/base/special/cospi.h"

stdlib_base_cospi( x )

Computes cos(πx) more accurately than cos(pi*x), especially for large x.

double out = stdlib_base_cospi( 0.5 );
// returns 0.0

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_cospi( const double x );

Examples

#include "stdlib/math/base/special/cospi.h"
#include <stdio.h>

int main( void ) {
    const double x[] = { 0.0, 0.523, 0.785, 1.047, 3.14 };

    double y;
    int i;
    for ( i = 0; i < 5; i++ ) {
        y = stdlib_base_cospi( x[ i ] );
        printf( "cospi(%lf) = %lf\n", x[ i ], y );
    }
}