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# C2: Trigonometrical equations

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1. Hi everyone, I’ve got a question that I really don’t know what to do with! I’d be really grateful if someone could give me some pointers.

So I thought it would be the identity that would be useful here. So I rearranged to
but then after that my mind froze and I really didn’t know what to do!
2. Multiply each term by cos x. Now it is possible to form a quadratic equation in sin x.
3. (Original post by Mr M)
Multiply each term by cos x. Now it is possible to form a quadratic equation in sin x.
4. you are going the right way. after where you got upto youget (3sinx/cosx)+2cosx=0 therefore (3sinx/cosx)=-2cosx so then 3sinx = -2cos^2x you should know what cos^2x is equivalent to and then when you substitute that you get a quadratic equation and get two values for sin x and then solve them for their given ranges. i dunno if im doing this right because you havent given the answer but i got sinx = -0.5 or 2
5. (Original post by dslc)
I bet you blurt out the punchlines to jokes too.
6. (Original post by Mr M)
I bet you blurt out the punchlines to jokes too.
Well actually, what you said was wrong.

It wasn't possible to form a quadratic without applying the information I added.

Apologies if I stole a little of your TSR thunder though.
7. (Original post by dslc)
Well actually, what you said was wrong.

It wasn't possible to form a quadratic without applying the information I added.

Apologies if I stole a little of your TSR thunder though.
"The butler did it!"
8. Thanks everyone for your help - that's really cleared it up for me
9. (Original post by dslc)
10. (Original post by kingfisher)

Perhaps consider starting a new thread however, given that they'd be unrelated to trigonometrical equations.

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