1 #include <u.h> 2 #include <libc.h> 3 4 /* 5 tanh(arg) computes the hyperbolic tangent of its floating 6 point argument. 7 8 sinh and cosh are called except for large arguments, which 9 would cause overflow improperly. 10 */ 11 12 double 13 tanh(double arg) 14 { 15 16 if(arg < 0) { 17 arg = -arg; 18 if(arg > 21) 19 return -1; 20 return -sinh(arg)/cosh(arg); 21 } 22 if(arg > 21) 23 return 1; 24 return sinh(arg)/cosh(arg); 25 } 26