If 5(tan 2 x−cos 2 x)=2cos2x+9, then the value of cos4x is

Question

asked Mar 9 in Uncategorized by Brainiak verified_user (11.1k points)
reopened Mar 10 by Brainiak

If 5(tan²x - cos²x)=2cos2x+9, then the value of cos4x is

A)-3/5

B)1/3

C)2/9

D)-7/9

from Jeemain 2014

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1 Answer

answered Mar 10 by Brainiak verified_user (11.1k points)
edited Mar 10 by Brainiak

See the below image ,

Solution