Source file src/pkg/math/asin.go

// Copyright 2009 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 math


/*
	Floating-point arcsine and arccosine.

	They are implemented by computing the arctangent
	after appropriate range reduction.
*/

// Asin returns the arcsine of x.
//
// Special cases are:
//	Asin(±0) = ±0
//	Asin(x) = NaN if x < -1 or x > 1
func Asin(x float64) float64 {
    if x == 0 {
        return x // special case
    }
    sign := false
    if x < 0 {
        x = -x
        sign = true
    }
    if x > 1 {
        return NaN() // special case
    }

    temp := Sqrt(1 - x*x)
    if x > 0.7 {
        temp = Pi/2 - satan(temp/x)
    } else {
        temp = satan(x / temp)
    }

    if sign {
        temp = -temp
    }
    return temp
}

// Acos returns the arccosine of x.
//
// Special case is:
//	Acos(x) = NaN if x < -1 or x > 1
func Acos(x float64) float64 { return Pi/2 - Asin(x) }