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# Verify the identity... AQA Maths C4 Jan 2013 watch

1. Verfiy the identity cotx - sin2x = cotx cos2x

I'm struggling to convert -sin2x to something meaningful and understand it! Can someone help please?

Thanks
2. (Original post by bekamop99)
Verfiy the identity cotx - sin2x = cotx cos2x

I'm struggling to convert -sin2x to something meaningful and understand it! Can someone help please?

Thanks
Sin2x = 2sinxcosx

If in doubt about trig, turn everything into sin or cos.
3. (Original post by SeanFM)
Sin2x = 2sinxcosx

If in doubt about trig, turn everything into sin or cos.
Thanks, I did that. Then what?
4. (Original post by bekamop99)
Thanks, I did that. Then what?
I would change the cot x into what that means, in terms of sin and cos. Then I would look at where I want to end up, and see that it is cot x times something, so I would factorise out the cot x (or the re-written version) and see what I am left with.

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