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- package math
- func Sincos(x float64) (sin, cos float64) {
- return sincos(x)
- }
- func sincos(x float64) (sin, cos float64) {
- const (
- PI4A = 7.85398125648498535156E-1
- PI4B = 3.77489470793079817668E-8
- PI4C = 2.69515142907905952645E-15
- M4PI = 1.273239544735162542821171882678754627704620361328125
- )
-
- switch {
- case x == 0:
- return x, 1
- case IsNaN(x) || IsInf(x, 0):
- return NaN(), NaN()
- }
-
- sinSign, cosSign := false, false
- if x < 0 {
- x = -x
- sinSign = true
- }
- j := int64(x * M4PI)
- y := float64(j)
- if j&1 == 1 {
- j += 1
- y += 1
- }
- j &= 7
- if j > 3 {
- j -= 4
- sinSign, cosSign = !sinSign, !cosSign
- }
- if j > 1 {
- cosSign = !cosSign
- }
- z := ((x - y*PI4A) - y*PI4B) - y*PI4C
- 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
- }
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