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# Maths question watch

for q3 I rearranged it to get

6 sin^2 x +7cos x -8 = 0
I solved it to get
(-7±root241)/12 = x

for q4 b I don't even know where to start.

q3:
https://imgur.com/a/TiMfq

q4:

Thank you.
2. (Original post by YourGoddamnRight)
6 sin^2 x +7cos x -8 = 0
I solved it to get
(-7±root241)/12 = x
You can't do that - sine and cos are two different functions in your equation. For quadratic formula to work, you need them both to be the same (and even then the output wouldnt be x=... !)

For Q4, begin by noting that and that
3. (Original post by RDKGames)
You can't do that - sine and cos are two different functions in your equation. For quadratic formula to work, you need them both to be the same (and even then the output wouldnt be x=... !)

For Q4, begin by noting that and that
So how would I go about making them the same, in q3
4. (Original post by YourGoddamnRight)
So how would I go about making them the same, in q3
Use an identity relating and
5. (Original post by RDKGames)
Use an identity relating and
sinx = tanx X cosx ?
6. (Original post by YourGoddamnRight)
sinx = tanx X cosx ?
No, the most basic one there is.
7. (Original post by RDKGames)
No, the most basic one there is.
the only other one i know is sin^2x + cos^2x = 1
8. (Original post by YourGoddamnRight)
the only other one i know is sin^2x + cos^2x = 1
So use it to get the eq. in terms of
9. (Original post by RDKGames)
So use it to get the eq. in terms of
but the sin and cos have different powers, what do i do about that?
10. (Original post by YourGoddamnRight)
but the sin and cos have different powers, what do i do about that?
Er... Yeah I think I'll just give it to you because you seem confused about this (something that you MUST be able to do without too much thought at A-Level)

Solve from there.
11. (Original post by RDKGames)
Er... Yeah I think I'll just give it to you because you seem confused about this (something that you MUST be able to do without too much thought at A-Level)

Solve from there.
Thank you so much

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Updated: February 7, 2018
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