function sincos( x ) {
	return assign( x, [ 0.0, 0.0 ], 1, 0 );
}
Simultaneously computes the sine and cosine of an angle measured in radians.

@param {number} x - input value (in radians)
@returns {Array<number>} sine and cosine

@example
var v = sincos( 0.0 );
// returns [ ~0.0, ~1.0 ]

@example
var v = sincos( 3.141592653589793/2.0 );
// returns [ ~1.0, ~0.0 ]

@example
var v = sincos( -3.141592653589793/6.0 );
// returns [ ~-0.5, ~0.866 ]

@example
var v = sincos( NaN );
// returns [ NaN, NaN ]