Which of the following points lies on the locus of the foot of perpendicular drawn upon any
Which of the following points lies on the locus of the foot of perpendicular drawn upon any
tangent to the ellipse, $\frac{x^{2}}{4}+\frac{y^{2}}{2}=1$ from any of its foci ?
Correct Option: 1
Let foot of perpendicular is $(\mathrm{h}, \mathrm{k})$

$\frac{x^{2}}{4}+\frac{y^{2}}{2}=1$ (Given)
$a=2, b=\sqrt{2}, e=\sqrt{1-\frac{2}{4}}=\frac{1}{\sqrt{2}}$
$\therefore$ Focus $(\mathrm{ae}, 0)=(\sqrt{2}, 0)$
Equation of tangent
$y=m x+\sqrt{a^{2} m^{2}+b^{2}}$
$y=m x+\sqrt{4 m^{2}+2}$
Passes throguh $(h, k)$
$(\mathrm{k}-\mathrm{mh})^{2}=4 \mathrm{~m}^{2}+2$ .................(1)
line perpendicular to tangent will have slope
$-\frac{1}{m}$
$y-0=-\frac{1}{m}(x-\sqrt{2})$
$m y=-x+\sqrt{2}$
$(h+m k)^{2}=2$ .............(2)
Add equaiton (1) and (2)
$\mathrm{k}^{2}\left(1+\mathrm{m}^{2}\right)+\mathrm{h}^{2}\left(1+\mathrm{m}^{2}\right)=4\left(1+\mathrm{m}^{2}\right)$
$\mathrm{h}^{2}+\mathrm{k}^{2}=4$
$\mathrm{x}^{2}+\mathrm{y}^{2}=4$ (Auxilary circle)
$\therefore(-1, \sqrt{3})$ lies on the locus.