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- package math
- func xatan(x float64) float64 {
- const (
- P0 = -8.750608600031904122785e-01
- P1 = -1.615753718733365076637e+01
- P2 = -7.500855792314704667340e+01
- P3 = -1.228866684490136173410e+02
- P4 = -6.485021904942025371773e+01
- Q0 = +2.485846490142306297962e+01
- Q1 = +1.650270098316988542046e+02
- Q2 = +4.328810604912902668951e+02
- Q3 = +4.853903996359136964868e+02
- Q4 = +1.945506571482613964425e+02
- )
- z := x * x
- z = z * ((((P0*z+P1)*z+P2)*z+P3)*z + P4) / (((((z+Q0)*z+Q1)*z+Q2)*z+Q3)*z + Q4)
- z = x*z + x
- return z
- }
- func satan(x float64) float64 {
- const (
- Morebits = 6.123233995736765886130e-17
- Tan3pio8 = 2.41421356237309504880
- )
- if x <= 0.66 {
- return xatan(x)
- }
- if x > Tan3pio8 {
- return Pi/2 - xatan(1/x) + Morebits
- }
- return Pi/4 + xatan((x-1)/(x+1)) + 0.5*Morebits
- }
- func libc_atan(float64) float64
- func Atan(x float64) float64 {
- return libc_atan(x)
- }
- func atan(x float64) float64 {
- if x == 0 {
- return x
- }
- if x > 0 {
- return satan(x)
- }
- return -satan(-x)
- }
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