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b) (integration by parts, twice)
V = pi ∫ y² dx
V = pi ∫x²sinx dx
u =x² ; v' = sinx
u' = 2x ; v =-cosx
∫ uv' = uv - ∫u'v
∫ x²sinx dx = x².(-cosx) - ∫ -2xcosx dx
∫ x²sinx dx = x².(-cosx) + 2 ∫ xcosx dx
∫ xcosx dx
let u=x ; v'=cosx
u' =1 ; v=sinx
∫ xcosx dx = xsinx -∫ sinx dx
∫ xcosx dx = xsinx + cosx
V = pi ∫x²sinx dx
V = pi {-x²cosx + 2[xsinx + cosx] }
limits are pi to 0.
V = pi (pi^2 -4)