Question

How do you know which function is the inner radius and which is the outer radius?

Answer 1

Step-by-step explanation:

Graphing them is the best way to tell (I put one from Desmos in th attachment scribbled on it a little to match our situation). Otherwise you'll just have to know which one is going to be where on the interval given; but that knowledge comes by graphing them a lot anyways.

Also remember to draw your strips/lines from the axis of revolution to the curves. The longer one will represent the outer radius of the volume and the shorter one the inner radius.

So:

1. Graph the functions.
2. Draw your strips/lines
3. Outer is longer, Inner is shorter

Comment with any questions.