Question

if cos 2 theta = sin 4 theta where 2 theta and 4 theta are acute angles find the value of theta​

Answer 1

$\huge\underline\bold {Answer:}$

cos2$\theta$ = sin4$\theta$

cos2$\theta$ = cos(90° – 40°)

2$\theta$ = 90° – 4$\theta$

➝ 2$\theta$ + 4$\theta$ = 90°

➝ 6$\theta$ = 90°

➝ $\theta$ = 15°

Hence, value of $\theta$ is 15°.

Some trigonometric identities:

(1) sin^2$\theta$

(2) sec^2 = tan^2 + 1

(3) cosec^2 = cot^2 + 1