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.
9 Floating point tangent.
12 // Tan returns the tangent of x.
13 func Tan(x float64) float64 {
14 // Coefficients are #4285 from Hart & Cheney. (19.74D)
16 P0 = -.1306820264754825668269611177e+5
17 P1 = .1055970901714953193602353981e+4
18 P2 = -.1550685653483266376941705728e+2
19 P3 = .3422554387241003435328470489e-1
20 P4 = .3386638642677172096076369e-4
21 Q0 = -.1663895238947119001851464661e+5
22 Q1 = .4765751362916483698926655581e+4
23 Q2 = -.1555033164031709966900124574e+3
32 x = x * (4 / Pi) /* overflow? */
52 temp := ((((P4*xsq+P3)*xsq+P2)*xsq+P1)*xsq + P0) * x
53 temp = temp / (((xsq+Q2)*xsq+Q1)*xsq + Q0)