golang phase 代码
文件路径：/src/math/cmplx/phase.go
/ Copyright 2010 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 cmplx
import "math"
/ Phase returns the phase (also called the argument) of x.
/ The returned value is in the range [-Pi, Pi].
func Phase(x complex128) float64 { return math.Atan2(imag(x), real(x)) }