PLs. help me answer this. It's all about ellipse. Thank you.?

Question

The ceiling of an overpass is a semi- ellipse, 5 ft. high and 60 ft. wide. Find the clearance at the right edge of a lane if the edge is 20 ft. from the middle.

Answer 1

The semi-minor axis b is 5 ft, the semi-major axis a is 30 ft. The equation for an ellipse centered on 0,0 is

x^2/a^2 + y^2/b^2 = 1

The lane position x is 20 ft

20^2 / 30^2 + y^2 / 5^2 = 1

solve for y:

y = 5*√[1 - 4/9]

y = 3.73 ft