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Prove the following : 8sin^4(1/2theta)-8...

Prove the following : `8sin^4(1/2theta)-8sin^2(1/2theta)+1=cos2theta`

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R.H.S. = `cos2theta=1-2sin^2theta`
=`1-2xx(2sin(theta/2)cos(theta/2))^2`
`1-8sin^2(theta/2)cos^2(theta/2)`
`1-8sin^2(theta/2)(1-sin^2(theta/2))`
`1-8sin^2(theta/2)+8sin^4(theta/2)` = L.H.S.
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MBD PUBLICATION-TRIGONOMETRIC FUNCTIONS-QUESTION BANK
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  2. Prove the following : (1+sinA-cosA)/(1+sinA+cosA) = tan A//2

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  3. Prove the following : 8sin^4(1/2theta)-8sin^2(1/2theta)+1=cos2theta

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