asin.go

Documentation: math

		 1  // Copyright 2009 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package math
		 6  
		 7  /*
		 8  	Floating-point arcsine and arccosine.
		 9  
		10  	They are implemented by computing the arctangent
		11  	after appropriate range reduction.
		12  */
		13  
		14  // Asin returns the arcsine, in radians, of x.
		15  //
		16  // Special cases are:
		17  //	Asin(±0) = ±0
		18  //	Asin(x) = NaN if x < -1 or x > 1
		19  func Asin(x float64) float64 {
		20  	if haveArchAsin {
		21  		return archAsin(x)
		22  	}
		23  	return asin(x)
		24  }
		25  
		26  func asin(x float64) float64 {
		27  	if x == 0 {
		28  		return x // special case
		29  	}
		30  	sign := false
		31  	if x < 0 {
		32  		x = -x
		33  		sign = true
		34  	}
		35  	if x > 1 {
		36  		return NaN() // special case
		37  	}
		38  
		39  	temp := Sqrt(1 - x*x)
		40  	if x > 0.7 {
		41  		temp = Pi/2 - satan(temp/x)
		42  	} else {
		43  		temp = satan(x / temp)
		44  	}
		45  
		46  	if sign {
		47  		temp = -temp
		48  	}
		49  	return temp
		50  }
		51  
		52  // Acos returns the arccosine, in radians, of x.
		53  //
		54  // Special case is:
		55  //	Acos(x) = NaN if x < -1 or x > 1
		56  func Acos(x float64) float64 {
		57  	if haveArchAcos {
		58  		return archAcos(x)
		59  	}
		60  	return acos(x)
		61  }
		62  
		63  func acos(x float64) float64 {
		64  	return Pi/2 - Asin(x)
		65  }
		66
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