Evaluate integral, don't use calculator.

I'll use the S as the sign for integral
S 4 sin (theta)d(theta) from pi/2 to pi

I know the answer is 4 because I enter it in on my calculator, but don't know the steps to get to the answer.

Please help.

1 answer

The steps are:
(1) compute the indefinite integral.
in this case it is -4 cos theta

(2) Compute the value of the indefinite integral at theta = pi and subtract the value at theta = pi/2.

That would be -4(-1) -0 = 4

You won't learn integral calculus without learning how to compute integrals.