JEE MAIN - Mathematics (2022 - 26th June Evening Shift - No. 10)
The locus of the mid point of the line segment joining the point (4, 3) and the points on the ellipse $${x^2} + 2{y^2} = 4$$ is an ellipse with eccentricity :
$${{\sqrt 3 } \over 2}$$
$${1 \over {2\sqrt 2 }}$$
$${1 \over {\sqrt 2 }}$$
$${1 \over 2}$$
Explanation
Let $$P(2\cos \theta ,\,\sqrt 2 \sin \theta )$$ be any point on ellipse $${{{x^2}} \over 4} + {{{y^2}} \over 2} = 1$$ and Q(4, 3) and let (h, k) be the mid point of PQ
then $$h = {{2\cos \theta + 4} \over 2},\,k = {{\sqrt 2 \sin \theta + 3} \over 2}$$
$$\therefore$$ $$\cos \theta = h - 2,\,\sin \theta = {{2k - 3} \over {\sqrt 2 }}$$
$$\therefore$$ $${(h - 2)^2} + {\left( {{{2k - 3} \over {\sqrt 2 }}} \right)^2} = 1$$
$$ \Rightarrow {{{{(x - 2)}^2}} \over 1} + {{{{\left( {y - {3 \over 2}} \right)}^2}} \over {{1 \over 2}}} = 1$$
$$\therefore$$ $$e = \sqrt {1 - {1 \over 2}} = {1 \over {\sqrt 2 }}$$
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