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// 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, in radians, of x.
//
// Special cases are:
// Asin(±0) = ±0
// Asin(x) = NaN if x < -1 or x > 1
func Asin(x float64) float64 {
if haveArchAsin {
return archAsin(x)
}
return asin(x)
}
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, in radians, of x.
//
// Special case is:
// Acos(x) = NaN if x < -1 or x > 1
func Acos(x float64) float64 {
if haveArchAcos {
return archAcos(x)
}
return acos(x)
}
func acos(x float64) float64 {
return Pi/2 - Asin(x)
}
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