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 21 func asin(x float64) float64 { 22 if x == 0 { 23 return x // special case 24 } 25 sign := false 26 if x < 0 { 27 x = -x 28 sign = true 29 } 30 if x > 1 { 31 return NaN() // special case 32 } 33 34 temp := Sqrt(1 - x*x) 35 if x > 0.7 { 36 temp = Pi/2 - satan(temp/x) 37 } else { 38 temp = satan(x / temp) 39 } 40 41 if sign { 42 temp = -temp 43 } 44 return temp 45 } 46 47 // Acos returns the arccosine, in radians, of x. 48 // 49 // Special case is: 50 // Acos(x) = NaN if x < -1 or x > 1 51 func Acos(x float64) float64 52 53 func acos(x float64) float64 { 54 return Pi/2 - Asin(x) 55 } 56
