cmath: use ** for exponentiation in comments

R=rsc
CC=golang-dev
https://golang.org/cl/831045

src/pkg/cmath/exp.go

@@ -47,7 +47,7 @@ import "math"
 //    DEC       -10,+10      8700       3.7e-17     1.1e-17
 //    IEEE      -10,+10     30000       3.0e-16     8.7e-17
 
-// Exp returns e^x, the base-e exponential of x.
+// Exp returns e**x, the base-e exponential of x.
 func Exp(x complex128) complex128 {
 	r := math.Exp(real(x))
 	s, c := math.Sincos(imag(x))

src/pkg/cmath/polar.go

@@ -5,7 +5,7 @@
 package cmath
 
 // Polar returns the absolute value r and phase θ of x,
-// such that x = r * e^θi.
+// such that x = r * e**θi.
 // The phase is in the range (-Pi, Pi].
 func Polar(x complex128) (r, θ float64) {
 	return Abs(x), Phase(x)

src/pkg/cmath/pow.go

@@ -42,7 +42,7 @@ import "math"
 // arithmetic   domain     # trials      peak         rms
 //    IEEE      -10,+10     30000       9.4e-15     1.5e-15
 
-// Pow returns x^y, the base-x exponential of y.
+// Pow returns x**y, the base-x exponential of y.
 func Pow(x, y complex128) complex128 {
 	modulus := Abs(x)
 	if modulus == 0 {

src/pkg/cmath/sqrt.go

@@ -81,9 +81,9 @@ func Sqrt(x complex128) complex128 {
 		b *= 0.25
 		scale = 2
 	} else {
-		a *= 1.8014398509481984e16 // 2^54
+		a *= 1.8014398509481984e16 // 2**54
 		b *= 1.8014398509481984e16
-		scale = 7.450580596923828125e-9 // 2^-27
+		scale = 7.450580596923828125e-9 // 2**-27
 	}
 	r := math.Hypot(a, b)
 	var t float64