Concept:For the parabola
x2=4ay, the latus rectum endpoints are
(±2a,a), and the triangle with the vertex has area
21×4a×a=2a2.
Explanation:Given parabola:
x2=48y.
Compare with standard form
x2=4ay.
So,
4a=48, hence
a=12.
Vertex of the parabola is
(0,0).
For
x2=4ay, the latus rectum is the line
y=a.
Thus, here
y=12.
Put
y=12 in the parabola:
x2=48(12)=576.
So
x=±24.
Ends of the latus rectum are
(−24,12) and
(24,12).
The triangle is formed by these two points and the vertex
(0,0).
Base of the triangle
=24−(−24)=48.
Height is the perpendicular distance from
(0,0) to
y=12, which is
12.
Area
=21×48×12=288 sq. units.
Answer:288 sq. units, i.e. Option B.