Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Prove: $\sin^2 3α - \sin^2α = \sin4α\sin2α $

Also, simplify: $ \sqrt{\dfrac {1+\cos6α} {2}} $

Any help would be appreciated.

share|improve this question

closed as off-topic by Thomas, martini, Trevor Wilson, azimut, user1337 Oct 9 '13 at 19:53

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question is missing context or other details: Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Thomas, martini, Trevor Wilson, azimut, user1337
If this question can be reworded to fit the rules in the help center, please edit the question.

1 Answer 1

up vote 1 down vote accepted

For the first use $$\sin(A+B)\sin(A-B)=\sin^2A-\sin^2B$$ (Proof)

For the second use $$\cos2A=2\cos^2A-1$$

share|improve this answer
    
You were right...now its fixed. –  Bak1139 Oct 9 '13 at 18:49
    
@Bak1139, so the answer is adjusted:) –  lab bhattacharjee Oct 9 '13 at 18:51
    
many Thanks mate –  Bak1139 Oct 10 '13 at 14:14
    
@Bak1139, my pleasure –  lab bhattacharjee Oct 10 '13 at 16:43

Not the answer you're looking for? Browse other questions tagged or ask your own question.