| 1 | /* |
| 2 | sinh(arg) returns the hyperbolic sign of its floating- |
| 3 | point argument. |
| 4 | |
| 5 | The exponential function is called for arguments |
| 6 | greater in magnitude than 0.5. |
| 7 | The result overflows and 'huge' is returned for |
| 8 | arguments greater than somewhat. |
| 9 | |
| 10 | A series is used for arguments smaller in magnitude than 0.5. |
| 11 | The coeffieients are #2029 from Hart & Cheney. (20.36D) |
| 12 | |
| 13 | cosh(arg) is computed from the exponential function for |
| 14 | all arguments. |
| 15 | */ |
| 16 | |
| 17 | double exp(); |
| 18 | |
| 19 | static double p0 -0.6307673640497716991184787251e+6; |
| 20 | static double p1 -0.8991272022039509355398013511e+5; |
| 21 | static double p2 -0.2894211355989563807284660366e+4; |
| 22 | static double p3 -0.2630563213397497062819489e+2; |
| 23 | static double q0 -0.6307673640497716991212077277e+6; |
| 24 | static double q1 0.1521517378790019070696485176e+5; |
| 25 | static double q2 -0.173678953558233699533450911e+3; |
| 26 | static double q3 1.0; |
| 27 | |
| 28 | double |
| 29 | sinh(arg) double arg; { |
| 30 | |
| 31 | double sign, temp, argsq; |
| 32 | |
| 33 | sign = 1; |
| 34 | if(arg < 0){ |
| 35 | arg = - arg; |
| 36 | sign = -1; |
| 37 | } |
| 38 | |
| 39 | if(arg > 21.){ |
| 40 | temp = exp(arg)/2; |
| 41 | return(sign*temp); |
| 42 | } |
| 43 | |
| 44 | if(arg > 0.5) { |
| 45 | temp = (exp(arg) - exp(-arg))/2; |
| 46 | return(sign*temp); |
| 47 | } |
| 48 | |
| 49 | argsq = arg*arg; |
| 50 | temp = (((p3*argsq+p2)*argsq+p1)*argsq+p0)*arg; |
| 51 | temp = temp/(((q3*argsq+q2)*argsq+q1)*argsq+q0); |
| 52 | return(sign*temp); |
| 53 | |
| 54 | } |
| 55 | |
| 56 | double |
| 57 | cosh(arg) double arg; { |
| 58 | |
| 59 | double temp; |
| 60 | |
| 61 | if(arg < 0) |
| 62 | arg = - arg; |
| 63 | |
| 64 | if(arg > 21.){ |
| 65 | temp = exp(arg)/2; |
| 66 | return(temp); |
| 67 | } |
| 68 | |
| 69 | temp = (exp(arg) + exp(-arg))/2; |
| 70 | return(temp); |
| 71 | } |