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C3 double angle formula equations

I have no idea what I'm doing, I don't get how to solve this equation. Can anyone help ? :s
It's solving from 0 to 360. Thanks.
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Original post by Tremmel
I have no idea what I'm doing, I don't get how to solve this equation. Can anyone help ? :s
It's solving from 0 to 360. Thanks.
Posted from TSR Mobile


Divide both sides by cos(2theta)
Reply 2
Original post by usycool1
Divide both sides by cos(2theta)


Could you expand further on that please? :smile:
Original post by Tremmel
Could you expand further on that please? :smile:


Tan(2theta) =2
2theta = arctan 2

Go from there, my friend

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Original post by Tremmel
Could you expand further on that please? :smile:


Of course. :smile:

So you have sin2θ=2cos2θ\sin 2\theta = 2\cos 2\theta.

You can divide both sides by cos2θ\cos 2\theta, and you hopefully know that
Unparseable latex formula:

\tan \theta = \dfrac{\sin\theta}{\cos\theta}}

... :smile:
Reply 5
Original post by QuantumSuicide
Tan(2theta) =2
2theta = arctan 2

Go from there, my friend

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Thanks! I didn't realise that before and now I feel dumb
Original post by usycool1
Divide both sides by cos(2theta)


Hold up a second. Isn't there a possibility that you could lose solutions if you do this?

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Original post by QuantumSuicide
Hold up a second. Isn't there a possibility that you could lose solutions if you do this?

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No, because cos(2theta) doesn't equal 0.
Reply 8
Original post by usycool1
No, because cos(2theta) doesn't equal 0.


I think 2 solutions were lost, the book states 4 solutions but using that method I can only get 2.
Original post by Tremmel
I think 2 solutions were lost, the book states 4 solutions but using that method I can only get 2.


What was the domain for theta that you were given?
Reply 10
Original post by ThatPerson
What was the domain for theta that you were given?


0<theta<360
Original post by Tremmel
0<theta<360


If 0<θ<360 0 < \theta < 360 , then ?<2θ<? ? < 2\theta < ? ?

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