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# Area under a curve / Trig Identity watch

1. http://qualifications.pearson.com/co...e_20130122.pdf

Question 5 C

I don't know how to square 3sin2x
The mark scheme says the answer to it is 9/2(1-cos4x)
I have no idea how it went to that.
Urgent help needed, exam tomorrow
2. (Original post by Regret786)
http://qualifications.pearson.com/co...e_20130122.pdf

Question 5 C

I don't know how to square 3sin2x
The mark scheme says the answer to it is 9/2(1-cos4x)
I have no idea how it went to that.
Urgent help needed, exam tomorrow
(3sin2x)2 = 9sin2(2x)

Now
cos 2A = 1 - 2sin2A
cos 4A = 1 - 2sin22A
2sin22A = 1 - cos4A

and hopefully you can finish it

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