Tanx cosx = 0
i believe you have to use the cancellation method. you turn tanx into sinx/cosx times cos but i dont know where to go from there

You're almost finished.

(sin/cos) times cos = 0

Look at the left side.  You could write it as (sin x cos) / cos = 0
and simply divide numerator and denominator by the cosine (cancel it).

Then what do you have left ? . . .  sin(x) = 0       Do I need to finish this for you ?