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Tricky Trig Question

Trouble with only 7(c)



Is there any easier way to do that other than breaking it down into cos⁡θ\cos{\theta} and sin⁡θ\sin{\theta} (which becomes something like a 4th degree polynomial)? I've considered rewritting it as:

2cos⁡22θ+2cos⁡2θ−1=cos⁡θ2\cos^2{2\theta} +2\cos{2\theta}-1=\cos{\theta}

But the left side doesn't seem to factorize, so I don't know if that's much help.
lSi9FRy.png11.4KB
Original post by SamKeene
...


I suspect a misprint in the question and the first term should be in theta, not 2theta.

Hasufel posted a nice method with just theta, but has since withdrawn it. I suspect he was correct though.

As it stands, it's rather horrible, particularly when consider in the light of the difficulty of the previous two parts..
Reply 2
Avatar for Zacken
Zacken
22
Original post by ghostwalker
I suspect a misprint in the question and the first term should be in theta, not 2theta.

Hasufel posted a nice method with just theta, but has since withdrawn it. I suspect he was correct though.

As it stands, it's rather horrible, particularly when consider in the light of the difficulty of the previous two parts..


I think you're right, seems to be a misprint, Wolfram Alpha gives absolutely horrendous answers to it. :smile:
Reply 3
Avatar for SamKeene
SamKeene
OP
11
Original post by ghostwalker
I suspect a misprint in the question and the first term should be in theta, not 2theta.

Hasufel posted a nice method with just theta, but has since withdrawn it. I suspect he was correct though.

As it stands, it's rather horrible, particularly when consider in the light of the difficulty of the previous two parts..


Original post by Zacken
I think you're right, seems to be a misprint, Wolfram Alpha gives absolutely horrendous answers to it. :smile:



Hmm thanks guys... it does seem like a misprint.

I posted another thread here with a question from the same exam, and earlier in the paper... which I suspect might be a misprint, could you check it out?
Reply 4
Avatar for Hasufel
Hasufel
16
Original post by Zacken
I think you're right, seems to be a misprint, Wolfram Alpha gives absolutely horrendous answers to it. :smile:


I`d just noticed the "2theta" in the squared term and thought "balls, i got it wrong" - but, i dunno now...

if it`s 2theta, the solutions are more hideous than Donattela Versace - allegedly - (covering myself legally!)

If it`s theta the solutions are basic and simple...
(edited 9 years ago)

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