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// Copyright 2009 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package math

/*

        Floating-point hyperbolic tangent.

        Sinh and Cosh are called except for large arguments, which

        would cause overflow improperly.

*/

// Tanh computes the hyperbolic tangent of x.

//

// Special cases are:

//      Tanh(±0) = ±0

//      Tanh(±Inf) = ±1

//      Tanh(NaN) = NaN

func Tanh(x float64) float64 {

        if x < 0 {

                x = -x

                if x > 21 {

                        return -1

                }

                return -Sinh(x) / Cosh(x)

        }

        if x > 21 {

                return 1

        }

        return Sinh(x) / Cosh(x)

}