math: make function documentation more regular

R=rsc, golang-dev
CC=golang-dev
https://golang.org/cl/5994043
diff --git a/src/pkg/math/asinh.go b/src/pkg/math/asinh.go
index 0defbb9..ff2de02 100644
--- a/src/pkg/math/asinh.go
+++ b/src/pkg/math/asinh.go
@@ -30,7 +30,7 @@
 //	         := sign(x)*log1p(|x| + x**2/(1 + sqrt(1+x**2)))
 //
 
-// Asinh(x) calculates the inverse hyperbolic sine of x.
+// Asinh returns the inverse hyperbolic sine of x.
 //
 // Special cases are:
 //	Asinh(±0) = ±0