Question 1023319
AC is a diagonal of the square base.
as such it's length would be sqrt(2^2 + 2^2) = sqrt(8).
the diagonal AC forms a triangle AEC of which EO is the altitude.
this triangle AEC, with its altitude of EO, forms 2 right triangles.
they are triangle AEO and triangle EOC.
the height of these triangles is 3.
the base of these triangles is sqrt(8)/2.
the hypotenuse of these triangles is equal to sqrt(3^2 + (sqrt(8)/2)^2).
this becomes sqrt(9 + 8/4) which becomes sqrt(36/4 + 8/4) which becomes sqrt(44/4) which becomes sqrt(44)/2 which becomes sqrt(4*11)/2 which becomes 2*sqrt(11)/2 which becomes sqrt(11).


you get:


length of AC is sqrt(8).
length of EC is sqrt(11).


the diagram below should help you visualize what's happening.


<img src = "http://theo.x10hosting.com/2016/030402.jpg" alt="$$$" </>