Q. 8

Find the maximum area of an isosceles triangle inscribed in the ellipse with its vertex at one end of the major axis.

Answer :

It is given that ellipse

Let the major axis be along the x – axis.1).

Let ABC be the triangle inscribed in the ellipse where vertex C is at (a,0).

Since, the ellipse is symmetrical w.r.t. x - axis and y - axis, we can assume the coordinates of A to be ( - x1,y1) and the coordinates of B to be ( - x1, - y1).

Now, we have y1 = ± 

Therefore, Coordinates of A and the coordinates of B

As the point(x1,y1) lies on the ellipse, the area of triangle ABC (A) is given by:

A =



But, x1 cannot be equal to a.

⇒ x1 =

y1 =


Also, when x1 = , then,

< 0

Then, the area is the maximum when x1 = .

Therefore, Maximum area of the triangle is given by:

A =

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RS Aggarwal - Mathematics