Processing Math: Done

From Förberedande kurs i matematik 1

When you cancel tanx on both sides of the equation you might lose those solutions that satisfy tanx=0. The equation to the right might therefore, potentially, have a reduced set of solutions. You should consequently use the arrow.

NB. It doesn't matter that it later turns out that both equations do in fact have the same set of solutions. It is what you know at the time that determines what kind of arrow you use.