Complementary Incomplete Gamma Function (Not in Base Package)

Computes the complementary incomplete gamma function. Details  

	x is the input argument.
	a is the upper limit of the incomplete complementary gamma integral.
	1 - g(x, a) returns the value of the complementary gamma function.

Complementary Incomplete Gamma Function Details

The following equation defines the complement of the incomplete gamma function.

The complement of the incomplete gamma function is related to the incomplete gamma function by the following identity.

The function is defined according to the following intervals for the input values.

For any positive real value of upper limit a, the function is defined for nonnegative real values of x.