function median( mu, s ) {
	return addon( mu, s );
}
Returns the median for a raised cosine distribution with location `mu` and scale `s`.

@private
@param {number} mu - location parameter
@param {PositiveNumber} s - scale parameter
@returns {number} median

@example
var y = median( 0.0, 1.0 );
// returns 0.0

@example
var y = median( 5.0, 2.0 );
// returns 5.0

@example
var y = median( NaN, 1.0 );
// returns NaN

@example
var y = median( 0.0, NaN );
// returns NaN

@example
var y = median( 0.0, 0.0 );
// returns NaN