Trigonometry

Geometry Level pending

Given that:

5 ( tan ⁡ 2 x − cos ⁡ 2 x ) = 2 cos ⁡ 2 x + 9 5(\tan^{2}x - \cos^{2}x )= 2\cos2x+9 .

Find the value of:

cos ⁡ 4 x \cos4x correct up to 7 digits of the decimal.


The answer is -0.7777778.

Rishabh Sood by Rishabh Sood , 20, India

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1 solution

Rishabh Sood
Jul 9, 2017

And, as -7/9=0.777...., so is the answer.

PS: this is an iit faculty approved solution.

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