I would write:

Differentiating with respect time time , we find:

Now plug in the given values:

So what do we get?

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- Nov 20th 2012, 01:12 AMMarkFLRe: I don't even know where to start...
I would write:

Differentiating with respect time time , we find:

Now plug in the given values:

So what do we get? - Nov 20th 2012, 01:16 AMtheunforgivenRe: I don't even know where to start...
I don't know how to plug in secant (squared) into my calculator... :S

EDIT: -59.99? (Worried) - Nov 20th 2012, 01:25 AMMarkFLRe: I don't even know where to start...
You shouldn't need to use you calculator. The given angle is a "special angle" for which we should know all of the trig functions at this angle.

What is ?

If you know this, then since you can invert, then square to get the value you want. - Nov 20th 2012, 01:26 AMtheunforgivenRe: I don't even know where to start...
- Nov 20th 2012, 01:30 AMMarkFLRe: I don't even know where to start...
Yes, so what do you get when you invert and square?

- Nov 20th 2012, 01:32 AMtheunforgivenRe: I don't even know where to start...
- Nov 20th 2012, 01:40 AMMarkFLRe: I don't even know where to start...
That is the correct final answer, but I was asking what you got when you invert and square the value you found for the cosine function.

- Nov 20th 2012, 01:46 AMtheunforgivenRe: I don't even know where to start...
Oh my bad. I got 0.66666666667 (Giggle)

- Nov 20th 2012, 01:51 AMMarkFLRe: I don't even know where to start...
What I mean is:

invert:

square:

Thus, we know:

- Nov 20th 2012, 01:57 AMtheunforgivenRe: I don't even know where to start...
Stupid me! But thank you, sir, I truly appreciate all your help. You are a true math master! *bows down*

- Nov 20th 2012, 02:00 AMMarkFLRe: I don't even know where to start...
Glad to be of assistance!