the whole is meant to be over 3

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- Aug 14th 2010, 10:05 PMlink0099quickly differentiate this please

the whole is meant to be over 3 - Aug 14th 2010, 10:06 PMProve It
You have

.

Start by expanding the brackets. You should be able to find the derivative term by term. - Aug 14th 2010, 10:16 PMlink0099
is it

zero is excluded as 0 for a length (in the original question cannot make sense) - Aug 14th 2010, 10:19 PMProve It
No, your expansion gives

but you haven't differentiated it yet... - Aug 14th 2010, 10:26 PMlink0099
ok i really gotta practice with pi in these eqn's.

for stat points v' = 0

therefore

0 doesnt make sense so 4 only? - Aug 14th 2010, 10:35 PMProve It
Your calculations are correct.

But it should be possible to say that if you don't have a radius you don't have a volume, so is definitely a minimum...