I have tried this question (http://img524.imageshack.us/img524/9539/scan0001pa1.png) a number of times and always use the formula(adsbygoogle = window.adsbygoogle || []).push({});

S = 2*pi*int( y*sqrt( (dx/dt)^2+(dy/dt)^2 ) dt

i always get S=6*pi*a^2[1/5*(sin t)^5] 0<t<pi, and because sin 0 = 0 and sin pi = 0 the answer i get is 0. If you were to replace the y in the equation with x then i get the correct answer but that would not be the formula for rotation about the x-axis.

Any help would be much appreciated.

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# Area Of The Surface Of Revolution

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