HL Maths question

littlneutralone

1995, Paper II Q8 (c) -

'express the height of the cylinder in terms of its radius'

Is the stupid two dimensional diagram supposed to help?
I'm royally stuck - there's a good chance this kind of Q will come up as part c this year too which is why I'm obsessing..anyone know how to do this? Or are there 1995 solutions available online? I've searched but no dice..

Thanks..

Peleus

littlneutralone wrote: »

1995, Paper II Q8 (c) -

'express the height of the cylinder in terms of its radius'

Is the stupid two dimensional diagram supposed to help?
I'm royally stuck - there's a good chance this kind of Q will come up as part c this year too which is why I'm obsessing..anyone know how to do this? Or are there 1995 solutions available online? I've searched but no dice..

Thanks..

These Qs are easy. The one you're talking about is pretty hard tho. I'm not sure if you're allowed express h in terms of r and V(volume). I think you just use pythagoras' theorem to work out as many of those lengths of the cone as you can and somehow get a relationship between h and r for the cyliner.

actually i might do this now and scan it on.

Cokehead Mother

Yes, the stupid two dimensional diagram is supposed to help.

You've got a big triangle. Split it in half. It's now 11 high and 4 wide.

Then you've got those two little triangles. They're h high and 4-r wide.

h/(4-r) = 11/4

Do you understand why? I'm sure you can finish it from here.

Peleus wrote: »

These Qs are easy. The one you're talking about is pretty hard tho. I'm not sure if you're allowed express h in terms of r and V(volume).

It says to write h in terms of r. So don't express it in terms of r and V if you want marks.

Fuascailt

Its similiar triangles. Did this in class, my teacher reckoned that if we got that it would say "Using similiar triangles..."

littlneutralone

Ahh..stupid two dimensional diagram has a purpose.

THANK YOU all, I'll go mess with that and see how I get on.

I spent half an hour drawing a [really beautiful] 3D diagram and half an hour staring at it. They say I lack spatial skills


edit..worked. Yeah baby..thanks again. 95 paper is the only one I have no solutions for..all other Q's were perfectly fine and I get stuck on the one I *have* to do, nice.

Peleus

ok i got it. took me a while because i went down the pythagoras road and fuqed up. similar triangles and equal angles is the way to go.

littlneutralone

Thanks again for that. I did it really slightly differently with the baby and giant triangles.

Soo similar triangles means the ratios will be the same? Ha, I can actually remember not getting them in first year.

And if they give you a diagram, even if it's stupid and 2-D you still use it? Wild..

MathsManiac

Stupid?

It would have been a lot harder to see the similar triangles if you had a 3D diagram.

N'est-ce pas?

littlneutralone

Oui-c'est-vrai. I'm just bitter and twisted because I'm incredibly terrible at interpreting questions..even if they give you nice hints..especially if they give you nice hints.

Anyway-thanks again, and good luck in the thing next week.

Timans

God almighty,

No way in hell I would have been able to answer that.

Hmm..