Question

find the measure of angle theta when theta is acute



no spamming or I WILL report it​

Answer 1

$2 { \cos }^{2} 5x = 1$

${ \cos }^{2} 5x = \frac{1}{2}$

$\cos(5x) = \frac{1}{ \sqrt{2} }$

$\cos(5x) = \cos(45)$

$5x = 45$

$x = 9$

this is because cos 45=1/√2