# the mother of all p2 volumes of rev. question

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15 years ago
#21
(Original post by hihihihi)
Find the volume when the following shaded region is rotated 360 degrees about the y-axis.

AAAAAAAAAAAAAAAAAAAAAH!

Y axis!? I am such a buffoon.. i've been trying for half an hour and I read the bloody question wrong.

poo.
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#22
(Original post by kimoni)
AAAAAAAAAAAAAAAAAAAAAH!

Y axis!? I am such a buffoon.. i've been trying for half an hour and I read the bloody question wrong.

poo.
yeah that's why mik1a's method doesn't work i think. you must integrate x^2 with respect to y and not the other way.
y= x²
=> x=√y
Vol. = Pi * ∫ (x²)dy
= pi * ∫ y dy
=pi*[ y²/2] between 1 and 0
etc.

y=2-x²
=> x=√(2-y)
Vol. = Pi * ∫ (x²)dy
= pi * ∫ (2-y) dy
= pi * [2y - y²/2] between 2 and 1.
etc.
0
15 years ago
#23
pheeeeew.
done it.

now to move on to something else!!
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