Prove that: cos22x-cos26x = sin 4x sin 8x - Vidyadip

Question

Prove that: cos²2x-cos²6x = sin 4x sin 8x

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Answer

We have L.H.S= cos²2x-cos²6x
[$\because $ cos²B - cos²A = sin (A+B) sin (A - B)]
= sin 8 x sin 4x = R.H.S.

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