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# Edexcel C3 Exercise 6D, Question 3 - Help watch

1. Given that cotx = -(Root3), and that 90<x<180, find the exact value of

a) sinx
b) cosx
2. Do cot^-1 (-Root3) in your calculator. Take the value of x between 90 and 180 that satisfies this. Put it back into a and b.
3. What have you gotten so far? Perhaps put some of your working here so far or your plan on what to do?

Anyway, I suggest you start by converting cotx to 1/tanx first to find the acute angle x. (Some algebraic rearranging should do the trick)

Then consider the quadrant you are given (90<x<180) and whether sinx and cosx are positive or negative in that quadrant.
4. (Original post by iAre Teh Lejend)
Given that cotx = -(Root3), and that 90<x<180, find the exact value of

a) sinx
b) cosx
.

Multiply by tan x and divide by .

a) using your calculator, do the inverse tan and then find sin x
b) do the same as in a) but find cos x.
5. Thanks, I realised how to do this straight after i posted this thread. I was having a dumb moment.

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Updated: October 1, 2011
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