diff options
Diffstat (limited to 'src/lib/math/tan.go')
| -rw-r--r-- | src/lib/math/tan.go | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/src/lib/math/tan.go b/src/lib/math/tan.go index fff36c67b..ddfe80d0f 100644 --- a/src/lib/math/tan.go +++ b/src/lib/math/tan.go @@ -4,25 +4,26 @@ package math +import "math" + /* * floating point tangent - * Coefficients are #4285 from Hart & Cheney. (19.74D) */ -const -( - p0 = -.1306820264754825668269611177e+5; - p1 = .1055970901714953193602353981e+4; - p2 = -.1550685653483266376941705728e+2; - p3 = .3422554387241003435328470489e-1; - p4 = .3386638642677172096076369e-4; - q0 = -.1663895238947119001851464661e+5; - q1 = .4765751362916483698926655581e+4; - q2 = -.1555033164031709966900124574e+3; - piu4 = .1273239544735162686151070107e+1; // 4/pi -) - export func Tan(arg float64) float64 { + // Coefficients are #4285 from Hart & Cheney. (19.74D) + const + ( + P0 = -.1306820264754825668269611177e+5; + P1 = .1055970901714953193602353981e+4; + P2 = -.1550685653483266376941705728e+2; + P3 = .3422554387241003435328470489e-1; + P4 = .3386638642677172096076369e-4; + Q0 = -.1663895238947119001851464661e+5; + Q1 = .4765751362916483698926655581e+4; + Q2 = -.1555033164031709966900124574e+3; + ) + flag := false; sign := false; x := arg; @@ -30,7 +31,7 @@ export func Tan(arg float64) float64 { x = -x; sign = true; } - x = x * piu4; /* overflow? */ + x = x * (4/Pi); /* overflow? */ var e float64; e, x = sys.modf(x); i := int32(e); @@ -50,8 +51,8 @@ export func Tan(arg float64) float64 { } xsq := x*x; - temp := ((((p4*xsq+p3)*xsq+p2)*xsq+p1)*xsq+p0)*x; - temp = temp/(((xsq+q2)*xsq+q1)*xsq+q0); + temp := ((((P4*xsq+P3)*xsq+P2)*xsq+P1)*xsq+P0)*x; + temp = temp/(((xsq+Q2)*xsq+Q1)*xsq+Q0); if flag { if(temp == 0) { |