"Sketch the graph of y=tan(x/2)

By solving the equation x/2=-pi/2
x=- pi
and the equation x/2=pi/2
x=pi..."

Before I go any further, I need to understand where these equations came from. Where does the pi come from out of thin air? What becomes of the tangent? Can you please explain why each step happens? That would be great, thanks.

tangent = opposite /adjacent

look what happens to "adjacent" as you go close to the y axis. Division by close to zero is big.