semi-major axis : 2.5 m
semi-minor axis : 1 m
coordinates of the center: C(0, 3)
Thus the equation of the ellipse is:
Because you only need the upper part of the ellipse you can solve for y to get the equation of a function:
The points A and B are 1 m from the wall: A(-1.5, e(1.5)) and B(1.5, e(1.5))
Because the ellipse is symmetric about the y-axis it is only necessary to calculate e(1.5).
I've got A(-1.5, 3.8), B(1.5, 3.8)