)
	// special cases
	switch {
	case IsNaN(x):
		return x
	case IsInf(x, 0) || x == 0:
		return 0
	}

	sign := false
	if x < 0 {
		x = -x
		sign = true
	}
	if x >= 2 {
		s, c := Sincos(x)
		ss := -s - c
		cc := s - c

		// make sure x+x does not overflow
		if x < MaxFloat64/2 {
			z := Cos(x + x)
			if s*c > 0 {
				cc = z / ss
			} else {
				ss = z / cc
			}
		}