If tan A × tan B = root under a-b/a+b then prove that (a-b cos 2A) × (a-b cos 2B)= a×a-b×b

If tan A × tan B = root under a-b/a+b then prove that (a-b cos 2A) ×

1.	If tan A × tan B = root under a-b/a+b then prove that (a-b cos 2A) × (a-b cos 2B)= a×a-b×b
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