code review 6589070: go-tour: add copyright notices

gotour/solutions/complexcube.go

+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package main
 
 import (
         "fmt"
         "math/cmplx"
 )
 
 const delta = 1e-10
 
 func Cbrt(x complex128) complex128 {
         z := x
         for {
                 n := z - (z*z*z-x)/(3*z*z)
                 if cmplx.Abs(n-z) < delta {
                         break
                 }
                 z = n
         }
         return z
 }
 
 func main() {
         const x = 2
         mine, theirs := Cbrt(x), cmplx.Pow(x, 1./3.)
         fmt.Println(mine, theirs, mine-theirs)
 }