Prove that (cos 2A - cos 2B)^2 + (sin 2A - sin 2B)^2=4sin^2(A-B)....please help me to solve this trigo question...thank u

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- September 27th 2012, 11:31 PMsharmalaplease help me to prove this...
Prove that (cos 2A - cos 2B)^2 + (sin 2A - sin 2B)^2=4sin^2(A-B)....please help me to solve this trigo question...thank u

- September 27th 2012, 11:40 PMMarkFLRe: please help me to prove this...
Hint: within the parentheses, use sum to product identities, and you will have it in a few steps.

- September 28th 2012, 12:44 AMsharmalaRe: please help me to prove this...
can anyone please show me the first step...please

- September 28th 2012, 02:02 AMSironRe: please help me to prove this...

Use

Can you proceed now? - September 28th 2012, 02:12 AMsharmalaRe: please help me to prove this...
im still having problem with this question....

- September 28th 2012, 04:51 AMSironRe: please help me to prove this...
- September 28th 2012, 05:12 AMSorobanRe: please help me to prove this...
Hello, sharmala!

We will need these two identities:

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Quote:

Expand the left side:

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- September 28th 2012, 06:46 AMSironRe: please help me to prove this...
In case you wanted to continue with the formulas of Simpson.