Explanation:
We apply the midpoint formula like so
C = (A+B)/2
C = (3pi+pi)/2
C = (4pi)/2
C = 2pi
This means 2pi is exactly halfway between pi and 3pi
This is similar to saying that 2 is halfway between 1 and 3. Think of the "pi" as "1pi", and we're effectively just looking at the coefficients.