Solution
For this case we have the following expression:
[tex]\sin x\cos x-3\cos x=0[/tex]We can take common factor and we got:
[tex]\cos x(\sin x-3)=0[/tex]Then we have two possibilities:
cos x = 0
that happens for:
[tex]x=\frac{\pi}{2}+2\pi\cdot n,\frac{3\pi}{2}+2\pi\cdot n[/tex]and the other possibility is:
sin x= 3 (No solution)
then the final answer is:
x= pi/2, 3pi/2
