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Wandering the Lacuna
That's what I just thought of. I'm reading through Keypad's answer from above, and I realise why. We need split up the integral - from 0 to 1, it's we use x2 = y (there's your bottom half), and from 1 to 2, it's x2 = 2-y (there's the top half). That fills the full integral, with limits from 0 to 2. Instead of just 0 to 1 combining both integrals. we have to do them separately, from 0 to 1 and 1 to 2 (did I mention these rotate with bits hanging low annoy me? 
). We work out the integral, rotate them, and add them. That will gives us the correct answer. So:
V = pi∫x2 dy
= pi[y2/2]10 + pi[2y - y2]21
= 1/2 pi + 1/2 pi
= pi units3
We had the right idea, but wrong execution. I'm tired after all that... I'm off to bed.
I_F
). We work out the integral, rotate them, and add them. That will gives us the correct answer. So:V = pi∫x2 dy
= pi[y2/2]10 + pi[2y - y2]21
= 1/2 pi + 1/2 pi
= pi units3
We had the right idea, but wrong execution. I'm tired after all that... I'm off to bed.
I_F
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