Let AB be the parabolic arch having O at the vertex and the vertical line OY as the axis.
The parabola open upwards
∴ Its equation is of the form ...(i)
Width of the arch, LM = 5 m
OM = 2.5 m
Height of the arch, BM = 10 m
∴ Co-ordinates of point B are (2.5, 10)
Since point B lies on the parabola
∴
∴ From (i), the equation of the parabola is:
or ...(ii)
We have to find the width PQ of the arch at a distance ON = 2 m from the vertex.
Let PQ = d NQ =
∴ Co-ordinates of point Q are
Putting it in (ii), we get
Hence, the width of the arch = d = or 2.23 (approx).
If a parabolic reflector is in diameter and 20 cm deep, find the distance of its focus S from the vertex.
An equilateral triangle is inscribed in a parabola y2 = 16x, where one vertex is at the vertex of the parabola. Find
(i) Length of each side of the triangle (ii) the area of the triangle