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# C3 IYGB Trig question help watch

1. I'm doing Paper Q of the IYGB papers and am having trouble with question 8b.

I get to the stage 2 theta - pi/3 = theta and then I can find the first solution, theta = pi/3. But after this I don't know how to find the other solutions.

Also, could a question like this be on an actual Edexcel C3 paper?

Thanks
2. (Original post by anonwinner)
I'm doing Paper Q of the IYGB papers and am having trouble with question 8b.

I get to the stage 2 theta - pi/3 = theta and then I can find the first solution, theta = pi/3. But after this I don't know how to find the other solutions.

Also, could a question like this be on an actual Edexcel C3 paper?

Thanks
Do you remember how to solve trig equations of the form ?

We have that but also (because fourth quadrant) .
3. (Original post by Zacken)
Do you remember how to solve trig equations of the form ?

We have that but also (because fourth quadrant) .
I use the CAST diagram method.

After I had found theta = pi/3 I then wrote theta = 2pi - pi/3 to find the solution in the fourth quadrant.

This resulted in theta = 5pi/3 but this is not a correct solution.
4. (Original post by anonwinner)
I use the CAST diagram method.

After I had found theta = pi/3 I then wrote theta = 2pi - pi/3 to find the solution in the fourth quadrant.

This resulted in theta = 5pi/3 but this is not a correct solution.
You found (the on your RHS is the "solution").

So you need to do: now.

5. (Original post by Zacken)
You found (the on your RHS is the "solution".

So you need to do: now.

Thanks I think I am starting to understand.

If this had been a typical C3 trig question (with theta on only 1 side of the equation), then my method would have worked. Why does it not work for this question?
6. (Original post by anonwinner)
Thanks I think I am starting to understand.

If this had been a typical C3 trig question (with theta on only 1 side of the equation), then my method would have worked. Why does it not work for this question?
Because is on both sides of the equation. You wouldn't get a question like that in an Edexcel exam though, or at least it would be very unlikely.
7. (Original post by Zacken)
Because is on both sides of the equation. You wouldn't get a question like that in an Edexcel exam though, or at least it would be very unlikely.
Okay thanks, I really hope it's not on the paper this year
8. (Original post by anonwinner)
Okay thanks, I really hope it's not on the paper this year
It won't be. Just remember, all your CAST stuff happens before manipulating the equation, if that makes sense.
9. CAST is what you support a limb after a fracture to aid recovery
10. (Original post by TeeEm)
CAST is what you support a limb after a fracture to aid recovery
Top banter m8

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