If 5(tan2x – cos2x) = 2cos 2x + 9, then the value of cos 4x is :

Question:

If $5\left(\tan ^{2} x-\cos ^{2} x\right)=2 \cos 2 x+9$, then the value of $\cos 4 x$ is :

  1. $-\frac{7}{9}$

  2. $-\frac{3}{5}$

  3. $\frac{1}{3}$

  4. $\frac{2}{9}$

Correct Option: 1

JEE Main Previous Year 1 Question of JEE Main from Mathematics Trigonometry chapter.
JEE Main Previous Year 2017

Solution:

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