cosm1

Compute cos(x) - 1.

Usage

var cosm1 = require( '@stdlib/math/base/special/cosm1' );

cosm1( x )

Computes cos(x) - 1, where cos is the cosine of a number (in radians). This function should be used instead of manually calculating cos(x) - 1 when the argument is near unity.

var PI = require( '@stdlib/constants/float64/pi' );

var v = cosm1( 0.0 );
// returns 0.0

v = cosm1( PI/4.0 );
// returns ~-0.293

v = cosm1( -PI/6.0 );
// returns ~-0.134

v = cosm1( NaN );
// returns NaN

Examples

var linspace = require( '@stdlib/array/base/linspace' );
var PI = require( '@stdlib/constants/float64/pi' );
var cosm1 = require( '@stdlib/math/base/special/cosm1' );

var x = linspace( 0.0, 2.0*PI, 100 );

var i;
for ( i = 0; i < x.length; i++ ) {
    console.log( cosm1( x[ i ] ) );
}

C APIs

Usage

#include "stdlib/math/base/special/cosm1.h"

stdlib_base_cosm1( x )

Computes cos(x) - 1, where cos is the cosine of a number (in radians). This function should be used instead of manually calculating cos(x) - 1 when the argument is near unity.

double out = stdlib_base_cosm1( 0.0 );
// returns 0.0

out = stdlib_base_cosm1( 3.141592653589793238 / 4.0 );
// returns ~-0.293

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_cosm1( const double x );

Examples

#include "stdlib/math/base/special/cosm1.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_cosm1( x[ i ] );
        printf( "cosm1(%lf) = %lf\n", x[ i ], y );
    }
}