sin4x-sin2x/sin2x=cos3x/cosx

i got left side equals right side..which is 1-4sin^2x

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- August 23rd 2008, 06:21 PMnithui need help proving this identity
sin4x-sin2x/sin2x=cos3x/cosx

i got left side equals right side..which is 1-4sin^2x - August 23rd 2008, 06:38 PMTKHunny
1) Please add parentheses to clarify meaning.

Is it as you have written it or did you mean (sin(4x)-sin(2x))/sin(2x)?

2) Please show your work. It's nice that you managed some result, but how did you do that?

3) When you get left side = right side, you are done.

Where does that leave us? - August 24th 2008, 05:37 AMSoroban
Hello, nithu!

Working from one side only (the recommended method) is difficult.

I worked on both sides and made them "meet in the middle" (as you did)

. . then devised a way to connect them.

Quote:

Prove: .

The right side is: .

. . . . .

Multiply by

. .

- August 24th 2008, 09:12 AMnithu
can u show me the left side and right side work...thx

- August 24th 2008, 12:11 PMSoroban
Hello, nithu!

For the left-side work, read**up**from the bottom of my solution.

You should be able to see how they "meet in the middle."