// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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/*
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Floating-point arcsine and arccosine.
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They are implemented by computing the arctangent
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after appropriate range reduction.
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*/
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// Asin returns the arcsine, in radians, of x.
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//
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// Special cases are:
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// Asin(±0) = ±0
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// Asin(x) = NaN if x < -1 or x > 1
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func Asin(x float64) float64
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func asin(x float64) float64 {
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if x == 0 {
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return x // special case
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}
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sign := false
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if x < 0 {
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x = -x
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sign = true
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}
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if x > 1 {
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return NaN() // special case
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}
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temp := Sqrt(1 - x*x)
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if x > 0.7 {
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temp = Pi/2 - satan(temp/x)
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} else {
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temp = satan(x / temp)
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}
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if sign {
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temp = -temp
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}
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return temp
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}
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// Acos returns the arccosine, in radians, of x.
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//
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// Special case is:
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// Acos(x) = NaN if x < -1 or x > 1
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func Acos(x float64) float64
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func acos(x float64) float64 {
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return Pi/2 - Asin(x)
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}
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