How Does Cannonball Trajectory Change with Height?

[popmop2]

Homework Statement

A cannon is placed at the bottom of a cliff 85 m high. If the cannon is fired straight upward, the cannonball just the reaches the top of the cliff.
a) Calculate the initial speed of the cannonball.
b) Suppose a second cannon is placed at the top of the cliff and fired horizontally with the same initial speed as part (a). Prove numerically that the range of this cannon is the same as the maximum range of the cannon from the base of the cliff.

Homework Equations

for a) v^2 = 2gh
for b) ymax = (v^2 sin^2 ∅)/2g

The Attempt at a Solution

for a) i got v = 40.8375 m/s

for b) i got ymax = 85 meters but that is only for the vertical part.

I am not sure how to find the numerically part

 

[haruspex]

for b) ymax = (v^2 sin^2 ∅)/2g

Not a useful equation for this question. Do you have any equations relating to range?