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C3 Trig Question

Managed to work it out - thank you!
(edited 12 years ago)
Reply 1
Start by factorising it. If it helps write u=cosecxu=\text{cosec}\, x and solve for uu first; then substitute back. You can rearrange it to get equations in sinx\sin x if that helps, and then you just solve for xx as normal.
Reply 2
re-write the problem but with y=cosec(x). You'll then have a nice easy quadratic that you can solve without thinking to get y=something. Then, substitute cosec(x) back in and then you just have some nice simple cosec(x) = something problems to solve. Yay!
2csc2x3cscx=02{\csc^2 x}-3\csc x = 0

Let y=csc x

Then you get:

2y23y=02y^2-3y=0
Original post by bertiejess
I did that, but when I typed it into the calculator, it didn't work?

Edit: would you say 1/cosecx = sin x and then flip 3/2?


Yea. That sounds right
Reply 5
Original post by bertiejess
I did that, but when I typed it into the calculator, it didn't work?

Edit: would you say 1/cosecx = sin x and then flip 3/2?


when you typed what into the calculator? You need to solve the quadratic in y, then solve each solution to get an x out.
Reply 6
can somene help me pleease

Given that:

cos(x+30) = 3 cos(x-30) , prove that,

tan x = - ''root 3''/2

then prove that: (1 - cos '2theta') / sin '2theta' = tan 'theta'

and verify that 'theta' = 180 is a solution of the equation sin 2'theta' = 2 - 2 cos2'theta'

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