One more:
Solve 
Remember the game on these... We know how to solve  
... So, let's do that. 
This 1 means that sine and cosine are the same! 

But, we needed to solve for x, not . Stick the 3x back in for the :
You can always check this solution on a graphing calculator by graphing
at the same time. They should intersect at  and every  
interval from there. 
TRY IT:
Solve 