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Let cos beta is the geometric mean betwe...

Let `cos beta` is the geometric mean between `sin alpha and cos alpha ` , where `0 lt alpha lt beta lt pi//2` , then `cos 2beta` is equal to

A

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

B

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

C

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

D

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

Text Solution

Verified by Experts

The correct Answer is:
A, B
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