tgamma

TGAMMA(3)		     libc math functions		    TGAMMA(3)



NAME
       tgamma, tgammaf, tgammal - true gamma function

SYNOPSIS
       #include <math.h>

       double tgamma(double x);
       float tgammaf(float x);
       long double tgammal(long double x);


DESCRIPTION
       The Gamma function is defined by

	Gamma(x) = integral from 0 to infinity of t^(x-1) e^-t dt

       It  is  defined for every real number except for nonpositive integers.
       For nonnegative integral m one has

	Gamma(m+1) = m!

       and, more generally, for all x:

	Gamma(x+1) = x * Gamma(x)

       For x < 0.5 one can use

	Gamma(x) * Gamma(1-x) = PI/sin(PI*x)

       This function returns the value of the Gamma function for the argument
       x.  It had to be called "true gamma function" since there is already a
       function gamma() that returns something else.

ERRORS
       An application wishing to check for error situations should set	errno
       to  zero	 and  call  feclearexcept(FE_ALL_EXCEPT) before calling these
       functions. On return, if errno is non-zero or  fetestexcept(FE_INVALID
       | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
       occurred.

       A range error occurs if x is too large.	A pole error occurs if	x  is
       zero.   A  domain  error	 (or  a pole error) occurs if x is a negative
       integer.

CONFORMING TO
       C99.

SEE ALSO
       lgamma(3), gamma(3)



GNU				  2002-08-10			    TGAMMA(3)