/x a-1 P(a,x) = | exp(-t) t dt /0

and

/inf a-1 Q(a,x) = | exp(-t) t dt /x

for a > 0. It is easy to see that Gamma(a) = P(a,x) + Q(a,x).

See all of incomplete gamma functions, no other writeups in this node.

Incomplete gamma functions are given by:

/x a-1 P(a,x) = | exp(-t) t dt /0

and

/inf a-1 Q(a,x) = | exp(-t) t dt /x

for a > 0. It is easy to see that Gamma(a) = P(a,x) + Q(a,x).