tgamma, tgammaf, tgammal - compute gamma function

Syntax	#include <math.h> C11 double tgamma(double x); float tgammaf(float x); long double tgammal(long double x); (End)
Description	These functions compute the mathematical gamma function for a given floating-point number x:
Return val.	tgamma(x)	Value of the gamma function if successful.
	HUGE_VAL HUGE_VALF HUGE_VALL	depending on the function type, if an error occurs. errno is set to indicate the error.
Errors	tgamma(), tgammaf() and tgammal() will fail if:
	ERANGE	Overflow; the return value is too large.
	EDOM	x is a non-positive integer.
See also	lgamma(), math.h.