as x approaches infinity (sinx)/x = 0
but for the question
sin(pi/2n) / (pi/2n)
as n approaches infinity
pi/2n approaches 0
so think of pi/2n as x
(sinx)/x = 1 where x is approaching 0
answer is 8pi/3 u^3
if you want to do it via shells rotated around the x axis you have to do shells for y=x/2 minus shells for y = sqrtx
V of a shell = 2pi (2y^2 - y^3) dy
Integral from 2 to 0 of 2y^2 - y^3 = 2pi [ 2y^3/3 - y^4/4]
= 2pi(16/3 - 4)
= 8pi/3
I'm bored, give me an estimate.
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