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# Prove: rot 1+sina / 1- sina = (sina/2 + cosa/2) / (sina/2 - cosa/2)? watch

1. 1. cosec? + 2cosec 2? / sec? = cot?/2

2. 1+tanatan2a = sec2a

3. 2sin? sin2?/ cos? + cos3? = tan2?tan?

4. sin3?/sin? - cos3?/cos? = 2

5. cos3?/cos? + sin3?/sin? = 4cos2?

6. (tan?/2 + cot ?/2) / (cot?/2 - tan?/2)

7. sin3?/cos? + cos3?/ sin? = 2cot2?

I was working on my assignment questions and I got stuck in those.. can you please help me !!

Thank you
2. The format of these is all the same -- you just need to apply identities. My advice is to convert everything into sines and cosines, and work from the more complicated-looking side to the more simple-looking side. I'm not going to give you the solutions to these problems, but good tricks to look out for are:

(i) Getting rid of s by using double-angle identities (unless they appear on both sides, in which case leave them there)
(ii) Getting rid of s by writing and using the angle-addition formulae
(iii) Doing (i) and (ii) in reverse (e.g. writing in terms of )
(iv) Looking out for things in the form
3. I do try doing these methods but it just doesn't work for me !;(
I do try doing these methods but it just doesn't work for me !;(
Well show your working! No-one here's going to do 7 questions for you.

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Updated: April 14, 2011
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