cosm1

Compute cos(x) - 1.

Installation

npm install @stdlib/math-base-special-cosm1

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 );
    }
}

See Also

• @stdlib/math-base/special/cos: compute the cosine of a number.

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

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Copyright

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