summaryrefslogtreecommitdiffstats
path: root/src/math/asin.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/math/asin.go')
-rw-r--r--src/math/asin.go67
1 files changed, 67 insertions, 0 deletions
diff --git a/src/math/asin.go b/src/math/asin.go
new file mode 100644
index 0000000..8e1b2ab
--- /dev/null
+++ b/src/math/asin.go
@@ -0,0 +1,67 @@
+// 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)
+}