<p>Will we ever be required to evaluate an equation after applying the shell method?</p>
<p>What about washer/disk method?</p>
<p>And cross-section??</p>
<p>No shell, only washer/disk. Yes cross-sections.</p>
<p>Is it OK to just stick the eq into my 89 and spit out a number? will i lose pts, b/c there's no work shown?</p>
<p>no shells? are you serious?</p>
<p>if i solve a problem using the shell method instead of the disk/washer method, will i be marked off?</p>
<p>by shell do you mean cylindrical method? because i think that's what my teacher called it. I'm not sure, but my teacher MIGHT have said we don't need to know it, but I 'm not sure so you should learn it... besides, it's not awful.
Washer method, be sure to know it, as most volume questions are based on that method.
And I don't believe I've heard of the cross-section method (if it's even a method), so could you explain that to me so I don't fail.</p>
<p>I think if you do shells, you're fine. I find it easier to do shells for problems when you're revolving around the y axis. The PR book even teaches you shells and has you do it for problems like those. </p>
<p>Volume questions are usually 3 points: 1 for the correct integral, 1 for the constant/limits, 1 for the answer. If you plug it into a calculator that can do it, but gives you only the answer, you'd get 1/3. I think they set it up that way so that people can't rely on their calculators for full credit.</p>
<p>But I'll have the entire equation...doesn't the correct integral have the limits/constants??</p>
<p>Also, when to use shells, and when to use washers/disks?</p>
<p>kr0nnik: as long as you write down the complete equation you're plugging into your calculator, you'll be fine</p>
<p>I guess b/c there's not that much you can grade on in calc, so they make up things to grade you on (like integrands and limits seperately, even though they're part of the same thing =P)</p>
<p>washer/disk - when area's bounded on the top and bottom and rotated around x axis OR when area's bounded on left and right and rotated around y axis</p>
<p>shells - when area's bounded on the top and bottom and rotated around y axis OR when area's bounded on left and right and rotated around x axis</p>
<p>But I guess you can use washer/disk for any case. =P</p>
<p>woh duh zhong wen zhwei hau</p>
<p>yeah they give points for what you write and what your answer is</p>
<p>not all equations are solveable by washer method, but all the ones that might be on the test will be, unless this cross section thing really is on the ab exam.</p>
<p>cross section isn't that bad at all.</p>
<p>they give you a three axis drawing, where there's a curve in the x and y, and shapes get stood up in the z direction. you basically take the base, multiply it by whatever height the shape has in the z direction, then multiply it by dy or dx, depending on w hich way the volume is going. I actually find it much easier than doing all the rotating crap.</p>
<p>and to OP, my friends in AB learned the shell method; I can't imagine my calc teacher teaching something that wasn't on the AP test to the AB class.</p>
<p>i really prefer disks unless it's a really complex shape. usually 2 curves = 2 radii = disk/washer method.</p>
<p>u dont HAVE to use shells but its easier
and yes to the rest</p>