Question

If cosx=25/169 then find cos2x

Answer 1

Answer:

-27311/28561

Step-by-step explanation:

Given :

$\mathrm{cosx = \dfrac{25}{169}}$

To find :

cos2x

Solution :

We know that,

$\boxed{\mathrm{cos2x = 2cos^2x - 1}}$

$\longmapsto \mathrm{cosx = \dfrac{25}{169}}$

Substituting in the formula, we get,

$\implies \mathrm{cos2x = 2\bigg(\dfrac{25}{169}\bigg)^2 -1}$

$\implies \mathrm{cos2x = \dfrac{1250 - 28561}{28561}}$

$\implies \mathrm{cos2x = \dfrac{-27311}{28561}}$

Hope it helps!!