Hi all ---

I'm trying to solve this question - and I've included the solution --

Question 1 ---I can't understand why you can divide by $\displaystyle \cos x$.

Because $\displaystyle 0 \leq x < 2 \pi$, you can have $\displaystyle \cos\left(\pi/2)\right = 0 = \cos\left(3\pi/2)\right$, right?

And we don't know what the x-values are. We haven't solved the equation yet?

Question 2 ---Also, how'd you know to divide by $\displaystyle \cos x$? Why not $\displaystyle \sin x$?

Thanks all.