function tan( x ) {
	return addon( x );
}
Evaluates the tangent of a number.

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

@example
var v = tan( 0.0 );
// returns ~0.0

@example
var v = tan( -3.141592653589793 / 4.0 );
// returns ~-1.0

@example
var v = tan( 3.141592653589793 / 4.0 );
// returns ~1.0

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