Question

if cos(x)=$\frac{8}{29}$ in Quadrant I, find cos(2x)=

Answer 1

Answer:

$- \frac{ 16}{29}$

Step-by-step explanation:

GIVEN:-

• $\cos(x) = \frac{8}{29}$

NEED TO FIND:-

• $\cos(2x)$

SOLUTION:-

$\cos(x) = \frac{8}{29}$

$x = { \cos }^{ - 1} ( \frac{8}{29} )$

$⇒ \cos(2x) = \cos(2\color{indigo}{{ \cos }^{ - 1} ( \frac{8}{29} )} \color{black})$

$⇒ \cos(2x) = 2 \times \frac{8}{29}$

$∴\cos(2x) = - \frac{16}{29}$

(minus because 2x is in Quadrant 2)

HOPE THAT HELPS!!