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If sin beta is the GM between sin alpha...

If `sin beta ` is the GM between `sin alpha and cos alpha, then cos 2beta=`

A

`2sin^(2)(pi/4-alpha)`

B

`2cos^(2)(pi/4-alpha)`

C

`2cos^(2)((3pi)/4+2alpha)`

D

`2sin^(2)(pi/4+alpha)`

Text Solution

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The correct Answer is:
A
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