Use a substitution to make it easier (eg. Sin(theta) =x). Then you get 7x^(2)- 36x+ 5=0 ........solve this quatratic trinomial. U should get x=1/7, x,=5. Therefore, sin(theta),=1/7, sin(theta)=5. Use sine inverse to find what theta is equal to.

( 7 sin theta - 1 )(sin theta - 5 ) = 0

(7x-1)(x-5)=0, where x=sin(theta), then sin(theta) = 1/7 or 5

(7 sin 𝝦 - 1) (sin 𝝦 - 5) = 0

sin 𝝦 = 1/7

𝝦 = 8.2 ⁰ , 171.8 ⁰