A series is used after range reduction.
Coefficients are #4285 from Hart & Cheney. (19.74D)
static double invpi
= 1.27323954473516268;
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;
double sign
, temp
, e
, x
, xsq
;
arg
= arg
*invpi
; /*overflow?*/
temp
= ((((p4
*xsq
+p3
)*xsq
+p2
)*xsq
+p1
)*xsq
+p0
)*x
;
temp
= temp
/(((1.0*xsq
+q2
)*xsq
+q1
)*xsq
+q0
);