The cable of a uniformly loaded suspension bridge hang in the form of a parabola.
The roadway which is horizontal and 100 m long, is supported by vertical wires attached to the cable, the longest wire being 30 m and the shortest being 6 m. Find the length of a supporting wire attached to a roadway 18 m from the middle.
Let point P be                Â
Givent that     Â
Squaring both sides, we get
                  Â
Squaring again, we get         Â
Hence, the locus of point P isÂ
which is the equation of an ellipse in the standard formÂ