function covercos( x ) {
	return addon( x );
}
Computes the coversed cosine.

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

@example
var v = covercos( 0.0 );
// returns 1.0

@example
var v = covercos( 3.141592653589793 / 2.0 );
// returns 2.0

@example
var v = covercos( -3.141592653589793 / 6.0 );
// returns 0.5

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