How do you evaluate definite integrals?

Answer 1

In order to evaluate a definite integral first find the indefinite integral. Then subtract the integral evaluated at the bottom number (usually the left endpoint) from the integral evaluated at the top number (usually the right endpoint).

For example, if I wanted the integral of x from 1 to 2 (written with 1 on the bottom and 2 on the top) I would first evaluate the integral:

the integral of x is (x^2)/2

Then I would subtract the integral evaluated at 1 from the integral evaluated at 2:

(2^2)/2-(1^2)/2 = 2-1/2 =3/2.