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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)`

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The correct Answer is:
D
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