# Parentheses

<p>So I have been working on area and volume of solids of revolution problems for AP Calculus by entering them into fnInt on my TI-83 Plus, and it always seems like I run into problems with knowing how many parentheses to use. Does anyone have any strategies that could help with this? Thanks.</p>

<p>If I were to be finding the area between two curves, say, from 0 to 1, here's what I would do (assuming that Y1 and Y2 hold the curves). </p>

<p>fnInt((Y1-Y2), X, 0, 1)</p>

<p>Does that help?</p>

<p>adding to what NewAccount said, you would enter your first function in Y1, second function in Y2. and then you would do math, fnInt(Y1-Y2), you can find Y1 and Y2 by pressing Vars on you calc and then going to Y-Vars-> Function</p>

<p>Oh, ok, thanks! I never thought to do it that way with the VARS key. That should help a lot with keeping the parentheses straight, and save time in typing the whole equation in again!</p>

<p>Can't believe you never knew that shortcut. :)</p>

<p>^actually, i solved all my volume questions last year on the ab calc test by doing all those parentheses. it was a pain lol. my bc calc teacher this year showed me how to do it...</p>

<p>Ouch! I've known about that since Algebra I. :p</p>

<p>I knew about the VARS key before, I just never used it for this type of problem. This is really going to save me some valuable time though, so the tip is much appreciated :)</p>

<p>It's been about a week since this thread was posted, and I have to say that the tip posted here has saved me a considerable amount of time and effort on each my practice exams since then. There is a area/volume question in the FRQs every year, and I have been able to nail each one with ease now that I don't have to worry about the parentheses issue I had earlier (I still can't believe I was never shown this before). Thanks so much for this extremely valuable tip! :)</p>