its vertical depth.
Take A D in position equal to
a c
.
On A D draw the square A B C D, and inscribe in it a circle.
Therefore, the circle so inscribed has the diameter of the top of the dish.
From A and D let fall verticals, A E, D H, each equal to
a d
.
Join E H, and describe square E F G H, which accordingly will be equal to the square A B C D, and be at the depth