Need fast!
why is the tan of (pi/2), undefined?

As the tangent function approaches 90 degrees (or pi / 2) it keeps increasing exponentially.  The tangent function =opposite / adjacent. 
As theta approaches 90 degrees, you can see the opposite side has to become longer and longer.  The tangent function is approaching infinity (but mathematicians don't like saying that) so it is technically "undefined".

Hi i’m back at my moms now i’ll call her when she can get there i’m gonna go first