math: document more special cases
Acosh, Asinh, Atanh, Ceil, Floor, Trunc, Mod and Remainder affected. These changes add some non-finite arguments and results (and -0.0 results).
R=rsc, golang-dev
CC=golang-dev
https://golang.org/cl/5469046
diff --git a/src/pkg/math/asinh.go b/src/pkg/math/asinh.go
index d697946..f786dd9 100644
--- a/src/pkg/math/asinh.go
+++ b/src/pkg/math/asinh.go
@@ -33,6 +33,7 @@
// Asinh(x) calculates the inverse hyperbolic sine of x.
//
// Special cases are:
+// Asinh(±0) = ±0
// Asinh(±Inf) = ±Inf
// Asinh(NaN) = NaN
func Asinh(x float64) float64 {
