Question

The line passing through the extremity $$A$$ of the major axis and extremity $$B$$ of the minor axis of the ellipse $${x^2} + 9{y^2} = 9$$   meets its auxiliary circle at the point $$M.$$  Then the area of the triangle with vertices at $$A,\,M$$  and the origin $$O$$ is-

A. $$\frac{{31}}{{10}}$$
B. $$\frac{{29}}{{10}}$$
C. $$\frac{{21}}{{10}}$$
D. $$\frac{{27}}{{10}}$$  
Answer :   $$\frac{{27}}{{10}}$$
Solution :
The given ellipse is $${x^2} + 9{y^2} = 9$$   or $$\frac{{{x^2}}}{{{3^2}}} + \frac{{{y^2}}}{{{1^2}}} = 1$$
Ellipse mcq solution image
So, that $$A\left( {3,\,0} \right)$$   and $$B\left( {0,\,1} \right)$$
$$\therefore $$ Equation of $$AB$$  is $$\frac{x}{3} + \frac{y}{1} = 1$$
or $$x + 3y - 3 = 0.....(1)$$
Also auxiliary circle of given ellipse is
$${x^2} + {y^2} = 9.....(2)$$
Solving equation (1) and (2), we get the point $$M$$ where line $$AB$$  meets the auxiliary circle.
Putting $$x=3-3y$$   from equation (1) in equation (2)
we get $${\left( {3 - 3y} \right)^2} + {y^2} = 9$$
$$\eqalign{ & \Rightarrow 9 - 18y + 9{y^2} + {y^2} = 9 \cr & \Rightarrow 10{y^2} - 18y = 0 \cr & \Rightarrow y = 0,\,\frac{9}{5}\,\,\,\,\,\,\, \Rightarrow x = 3,\,\frac{{ - 12}}{5} \cr} $$
Clearly $$M\left( {\frac{{ - 12}}{5},\,\frac{9}{5}} \right)$$
$$\therefore $$ Area of \[\Delta OAM = \frac{1}{2}\left| \begin{array}{l} \,\,\,0\,\,\,\,\,\,\,\,\,\,0\,\,\,\,1\\ \,\,\,3\,\,\,\,\,\,\,\,\,\,0\,\,\,\,1\\ \frac{{ - 12}}{5}\,\,\,\frac{9}{5}\,\,\,1 \end{array} \right| = \frac{{27}}{{10}}\]

Releted MCQ Question on
Geometry >> Ellipse

Releted Question 1

Let $$E$$ be the ellipse $$\frac{{{x^2}}}{9} + \frac{{{y^2}}}{4} = 1$$   and $$C$$ be the circle $${x^2} + {y^2} = 9.$$   Let $$P$$ and $$Q$$ be the points $$\left( {1,\,2} \right)$$  and $$\left( {2,\,1} \right)$$  respectively. Then-

A. $$Q$$ lies inside $$C$$ but outside $$E$$
B. $$Q$$ lies outside both $$C$$ and $$E$$
C. $$P$$ lies inside both $$C$$ and $$E$$
D. $$P$$ lies inside $$C$$ but outside $$E$$
Releted Question 2

The radius of the circle passing through the foci of the ellipse $$\frac{{{x^2}}}{{16}} + \frac{{{y^2}}}{9} = 1,$$   and having its centre at $$\left( {0,\,3} \right)$$  is-

A. $$4$$
B. $$3$$
C. $$\sqrt {\frac{1}{2}} $$
D. $$\frac{7}{2}$$
Releted Question 3

The area of the quadrilateral formed by the tangents at the end points of latus rectum to the ellipse $$\frac{{{x^2}}}{9} + \frac{{{y^2}}}{5} = 1,$$    is-

A. $$\frac{{27}}{4}\,\,{\text{sq}}{\text{.}}\,{\text{units}}$$
B. $$9\,\,{\text{sq}}{\text{.}}\,{\text{units}}$$
C. $$\frac{{27}}{2}\,\,{\text{sq}}{\text{.}}\,{\text{units}}$$
D. $$27\,\,{\text{sq}}{\text{.}}\,{\text{units}}$$
Releted Question 4

If tangents are drawn to the ellipse $${x^2} + 2{y^2} = 2,$$   then the locus of the mid-point of the intercept made by the tangents between the coordinate axes is-

A. $$\frac{1}{{2{x^2}}} + \frac{1}{{4{y^2}}} = 1$$
B. $$\frac{1}{{4{x^2}}} + \frac{1}{{2{y^2}}} = 1$$
C. $$\frac{{{x^2}}}{2} + \frac{{{y^2}}}{4} = 1$$
D. $$\frac{{{x^2}}}{4} + \frac{{{y^2}}}{2} = 1$$

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Ellipse


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