The gamma function extends the factorial: Gamma(n) = (n - 1)! for whole numbers, with Gamma(n + 1) = n Gamma(n) and Gamma(1/2) = root(pi). The beta function is B(m, n) = integral from 0 to 1 of x^(m-1) (1 - x)^(n-1) dx = Gamma(m) Gamma(n) / Gamma(m + n).
Problem 1. Find Gamma(5/2). Use the recurrence twice: Gamma(5/2) = (3/2)(1/2) Gamma(1/2) = 0.75 root(pi) = 0.75 x 1.7725 = 1.3293.
Problem 2. Evaluate the integral from 0 to 1 of x(1 - x)^2 dx using beta. Here m = 2 and n = 3, so B(2, 3) = Gamma(2) Gamma(3) / Gamma(5) = (1 x 2)/24 = 1/12 = 0.0833. Expanding and integrating directly gives 1/2 - 2/3 + 1/4 = 1/12, the same answer.
Problem 3. Evaluate the integral from 0 to pi/2 of sin^4(theta) d(theta). The standard form is (1/2) B(5/2, 1/2) = (1/2) Gamma(5/2) Gamma(1/2) / Gamma(3) = (1/2)(0.75 pi)/2 = 3 pi/16 = 0.589.
| Value | Result |
|---|
| Gamma(1) | 1 |
| Gamma(1/2) | root(pi) = 1.7725 |
| Gamma(5/2) | 0.75 root(pi) = 1.3293 |
| Gamma(5) | 4! = 24 |
| B(1/2, 1/2) | pi |