Hello, Zhang Yu's gamma function integral formula is in lecture 36 and lecture 7 on the concept and calculation of unary function integral.

For example, γ (α) = ∫. +∞ x (a- 1) e-xdx (a > 0) is a gamma function. So there is γ (n+ 1) = n!

Recursive formula can be established by using partial integral formula.

γ(α+ 1)=αγ(α)，α& gt； 0。

I wish you a happy study.