a = horizontal distance to this point

V = total speed of the projectile

mgh = initial mV_vertical^2/2

Initial mV_vertical^2/2 = mV^2/2 – mV_horizontal^2/2

V_horizontal = a / time to the top

time to the top = V/g

Ah, I think I’ve got it!

If you fire a projectile at a 45 degree angle from a position ‘a’ above the horizontal plane then ‘h’ is the approximate horizontal distance travelled.

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