1 files changed, 69 insertions, 0 deletions
diff --git a/src/math/sincos.go b/src/math/sincos.go
new file mode 100644
index 000000000..718030319
--- /dev/null
+++ b/src/math/sincos.go
@@ -0,0 +1,69 @@
+// Copyright 2010 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
+
+// Coefficients _sin[] and _cos[] are found in pkg/math/sin.go.
+
+// Sincos returns Sin(x), Cos(x).
+//
+// Special cases are:
+//	Sincos(±0) = ±0, 1
+//	Sincos(±Inf) = NaN, NaN
+//	Sincos(NaN) = NaN, NaN
+func Sincos(x float64) (sin, cos float64)
+
+func sincos(x float64) (sin, cos float64) {
+	const (
+		PI4A = 7.85398125648498535156E-1                             // 0x3fe921fb40000000, Pi/4 split into three parts
+		PI4B = 3.77489470793079817668E-8                             // 0x3e64442d00000000,
+		PI4C = 2.69515142907905952645E-15                            // 0x3ce8469898cc5170,
+		M4PI = 1.273239544735162542821171882678754627704620361328125 // 4/pi
+	)
+	// special cases
+	switch {
+	case x == 0:
+		return x, 1 // return ±0.0, 1.0
+	case IsNaN(x) || IsInf(x, 0):
+		return NaN(), NaN()
+	}
+
+	// make argument positive
+	sinSign, cosSign := false, false
+	if x < 0 {
+		x = -x
+		sinSign = true
+	}
+
+	j := int64(x * M4PI) // integer part of x/(Pi/4), as integer for tests on the phase angle
+	y := float64(j)      // integer part of x/(Pi/4), as float
+
+	if j&1 == 1 { // map zeros to origin
+		j += 1
+		y += 1
+	}
+	j &= 7     // octant modulo 2Pi radians (360 degrees)
+	if j > 3 { // reflect in x axis
+		j -= 4
+		sinSign, cosSign = !sinSign, !cosSign
+	}
+	if j > 1 {
+		cosSign = !cosSign
+	}
+
+	z := ((x - y*PI4A) - y*PI4B) - y*PI4C // Extended precision modular arithmetic
+	zz := z * z
+	cos = 1.0 - 0.5*zz + zz*zz*((((((_cos[0]*zz)+_cos[1])*zz+_cos[2])*zz+_cos[3])*zz+_cos[4])*zz+_cos[5])
+	sin = z + z*zz*((((((_sin[0]*zz)+_sin[1])*zz+_sin[2])*zz+_sin[3])*zz+_sin[4])*zz+_sin[5])
+	if j == 1 || j == 2 {
+		sin, cos = cos, sin
+	}
+	if cosSign {
+		cos = -cos
+	}
+	if sinSign {
+		sin = -sin
+	}
+	return
+}