/*	floating point tangent 	A series is used after range reduction.	Coefficients are #4285 from Hart & Cheney. (19.74D) */ #include <u.h>#include <libc.h> static double p0	 = -0.1306820264754825668269611177e+5;static double p1	  = 0.1055970901714953193602353981e+4;static double p2	 = -0.1550685653483266376941705728e+2;static double p3	  = 0.3422554387241003435328470489e-1;static double p4	  = 0.3386638642677172096076369e-4;static double q0	 = -0.1663895238947119001851464661e+5;static double q1	  = 0.4765751362916483698926655581e+4;static double q2	 = -0.1555033164031709966900124574e+3; doubletan(double arg){	double temp, e, x, xsq;	int flag, sign, i; 	flag = 0;	sign = 0;	if(arg < 0){		arg = -arg;		sign++;	}	arg = 2*arg/PIO2;   /* overflow? */	x = modf(arg, &e);	i = e;	switch(i%4) {	case 1:		x = 1 - x;		flag = 1;		break; 	case 2:		sign = !sign;		flag = 1;		break; 	case 3:		x = 1 - x;		sign = !sign;		break; 	case 0:		break;	} 	xsq = x*x;	temp = ((((p4*xsq+p3)*xsq+p2)*xsq+p1)*xsq+p0)*x;	temp = temp/(((xsq+q2)*xsq+q1)*xsq+q0); 	if(flag) {		if(temp == 0)			return NaN();		temp = 1/temp;	}	if(sign)		temp = -temp;	return temp;}