Recent content by mathFun

This makes perfect sense! Thank you so much! I really get it now! :D

But why does it work for say, doing the disk method then? In the disk method you are using dx, rather than ds. I guess that's what's confusing me about the whole thing is trying to understand why it works for the disk method, but when switching to surface area the dx approach doesn't work. Is...

Maybe I'm describing it wrong. For example, here is the equation I'm talking abouthttp://curvebank.calstatela.edu/arearev/arearev.htm I guess I don't understand why you can't just go∫2(pi)f(x)dx Because 2(pi)f(x) would be circumference of a circle of radius f(x) and you'd be multiplying these...

So if we are looking to find the surface area of a solid of revolution formed by rotating a curve about a line, we can use the following: S = ∫2(pi)yds (if rotating about the x-axis) FOr example, say our curve is y=x2 and we want to find the surface area of the solid of revolution...

hmm... I guess I got to just keep thinking about this and eventually it will make sense. :/

I always see the example f(x,y)={xy/(x2+y2) if (x,y) =/= (0,0) and 0 if (x,y)=(0,0)} given as the example of a function where the partial derivatives exist at the origin but are not continuous there. I have a difficult time wrapping my head around this and was hoping someone could...

Hey guys this question is going to sound pretty dumb, but I never learned how to do this. What if I want to find say, cos(pi/5) but I don't have a calculator? Even if I did have a calculator, I want it in nice values, like square roots, rather than decimals anyway. If I have something...