function cosine2( mu, s ) {
		if (
			isnan( mu ) ||
			isnan( s ) ||
			s <= 0.0
		) {
			return NaN;
		}
		return cosine0( rand, mu, s );
	}
Returns a pseudorandom number drawn from a raised cosine distribution.

@private
@param {number} mu - mean
@param {PositiveNumber} s - scale parameter
@returns {number} pseudorandom number

@example
var v = cosine2( 0.0, 2.0 );
// returns <number>

@example
var v = cosine2( 0.0, -1.0 );
// returns NaN