Beta takes as argument two reals a,b.
Beta returns the value of the β function at a,b ∈ ℝ, defined by :
|tx−1 (1−t)y−1 =|
Remarkable values :
Beta(x,y) is defined for x and y positive reals
(to insure the convergence of the integral) and by
prolongation for x and y if they are not negative integers.