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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)
}