Here's the question you clicked on:
Jaydam
4 cos θ sin θ + 3 cos θ = 0
after getting it in the form a*b=0 Set both factors equal to 0 a=0 or b=0
Or, is that the problem you are having? Are you having trouble seeing that 4cos(theta)sin(theta) and 3cos(theta) have a common factor?