function cosm1( x ) {
	return addon( x );
}
Computes the cosine of a number minus one.

@private
@param {number} x - input value (in radians)
@returns {number} cosine minus one

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

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

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

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

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

@example
var v = cosm1( NaN );
// returns NaN