
#20
Dec212, 01:00 PM

P: 147





#21
Dec312, 12:54 AM

P: 147

I think I got it now.
Let's say I'm trying to find the circumference and area of a circle by using rectangles to approximate. As the no. of rectangles approaches infinity, their combined height will always be equal to the diameter, and will never approximate the circumference. However, the combined area of those rectangles will approximate the area of the circle. This is why dz works for volume and not area integrals. It's a geometric proof, but how do we prove it mathematically? 



#23
Mar1513, 06:59 AM

P: 700

I am sorry. You ought to find moment of inertia of hollow sphere ? There are two ways: 1. Integration (difficult) 2. Coordinate geometry (easy!).. which I think you have been told here. 


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