Question

find the value of cos 2x when sin x=9/10​

Answer 1

Answer:

cos 2x = -0.62

Step-by-step explanation:

We have sin x = 9/10 = 0.9

Therefore,

${ \sin }^{2} (x) = 0.81$

Using,

${sin}^{2} (x) + {cos}^{2} (x) = 1 \\ {cos}^{2} (x) = \frac{19}{100}$

We know,

$\cos(2x) = {cos}^{2} (x) - {sin}^{2} (x) \\ \cos(2x) = \frac{19}{100} - \frac{81}{100} \\ \cos(2x) = - 0.62$

Answer 2

Answer:

answer is above

hope it's useful