go/src/math/cmplx/tan.go

// Tan returns the tangent of x.
func Tan(x complex128) complex128 { … }

// Tanh returns the hyperbolic tangent of x.
func Tanh(x complex128) complex128 { … }

// reducePi reduces the input argument x to the range (-Pi/2, Pi/2].
// x must be greater than or equal to 0. For small arguments it
// uses Cody-Waite reduction in 3 float64 parts based on:
// "Elementary Function Evaluation:  Algorithms and Implementation"
// Jean-Michel Muller, 1997.
// For very large arguments it uses Payne-Hanek range reduction based on:
// "ARGUMENT REDUCTION FOR HUGE ARGUMENTS: Good to the Last Bit"
// K. C. Ng et al, March 24, 1992.
func reducePi(x float64) float64 { … }

// Taylor series expansion for cosh(2y) - cos(2x)
func tanSeries(z complex128) float64 { … }

// Cot returns the cotangent of x.
func Cot(x complex128) complex128 { … }