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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 sine and cosine. The exponential func is called for arguments greater in magnitude than 0.5. A series is used for arguments smaller in magnitude than 0.5. Cosh(x) is computed from the exponential func for all arguments. */ // Sinh returns the hyperbolic sine of x. func Sinh(x float64) float64 { // The coefficients are #2029 from Hart & Cheney. (20.36D) const ( P0 = -0.6307673640497716991184787251e+6 P1 = -0.8991272022039509355398013511e+5 P2 = -0.2894211355989563807284660366e+4 P3 = -0.2630563213397497062819489e+2 Q0 = -0.6307673640497716991212077277e+6 Q1 = 0.1521517378790019070696485176e+5 Q2 = -0.173678953558233699533450911e+3 ) sign := false if x < 0 { x = -x sign = true } var temp float64 switch true { case x > 21: temp = Exp(x) / 2 case x > 0.5: temp = (Exp(x) - Exp(-x)) / 2 default: sq := x * x temp = (((P3*sq+P2)*sq+P1)*sq + P0) * x temp = temp / (((sq+Q2)*sq+Q1)*sq + Q0) } if sign { temp = -temp } return temp } // Cosh returns the hyperbolic cosine of x. func Cosh(x float64) float64 { if x < 0 { x = -x } if x > 21 { return Exp(x) / 2 } return (Exp(x) + Exp(-x)) / 2 }