2 sin^2(theta) - 7 sin(theat) = -3

is a quadratic in sin(theta). Solve this quadratic using to quadratic formula

to get sin(theta) = 1/2 or 3. Now sin(theta)=3 has no solution for theta in

the given range, so we are left with:

sin(theta) = 1/2, for theta in (0, 360] degrees, which you should be able to do

RonL