Hi guys! I've been working on this for a while:

I've restarted twice and have gotten to the same step with both:

-6 sinx - sin^2x - 5 = 0

I know I need to set the y(prime) equal to 0, so I used the quotient rule and then the -sin^2 x - cos^2 x = -1 identity and seem to have hit some sort of cul-de-sac, as it were! Any guidance is appreciated!