| // 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 |
| |
| |
| /* |
| * Sinh(x) returns the hyperbolic sine of x |
| * |
| * 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; |
| } |