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If 5(tan^2x - cos^2x)=2cos 2x + 9, then ...

If `5(tan^2x - cos^2x)=2cos 2x + 9`, then the value of cos4x is

A

`-(3)/(5)`

B

`1/3`

C

`2/9`

D

`-(7)/(9)`

Text Solution

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The correct Answer is:
D
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