The formula of gamma function for postgraduate entrance examination is γ (x) = ∫ 0 ∞ TX 1edtt. (x >； 0)。 When the variable of the equation is a positive integer, the value of the equation is the factorial of the positive integer. In postgraduate mathematics, we often use gamma function to solve some common integrals, especially in the topic of probability.

Origin:

1728, Goldbach was considering the interpolation of series. Generally speaking, the definition of general term formula of series is extended from integer set to real number set. For example, the sequence 1, 4, 9, 16 can be naturally expressed by the general formula n, even if n is a real number. Sometimes, this general formula is also well defined.

Intuitively, a smooth curve y=x can be found through all integer points (n, n), so that the formula defined on the integer set can be extended to the real set.