Gujarati
10-2. Parabola, Ellipse, Hyperbola
medium

If the normal at any point $P$ on the ellipse cuts the major and minor axes in $G$ and $g$ respectively and $C$ be the centre of the ellipse, then

A

${a^2}{(CG)^2} + {b^2}{(Cg)^2} = {({a^2} - {b^2})^2}$

B

${a^2}{(CG)^2} - {b^2}{(Cg)^2} = {({a^2} - {b^2})^2}$

C

${a^2}{(CG)^2} - {b^2}{(Cg)^2} = {({a^2} + {b^2})^2}$

D

None of these

Solution

(a) Let at a point $({x_1},{y_1})$ normal will be

$\frac{{(x – {x_1}){a^2}}}{{{x_1}}} = \frac{{(y – {y_1}){b^2}}}{{{y_1}}}$

At $G,\,\,y = 0$

==> $x = CG = \frac{{{x_1}({a^2} – {b^2})}}{{{a^2}}}$

At $g,\,\,\,x = 0$

==> $y = Cg = \frac{{{y_1}({b^2} – {a^2})}}{{{b^2}}}$

$\frac{{x_1^2}}{{{a^2}}} + \frac{{y_1^2}}{{{b^2}}} = 1$

==> ${a^2}{(CG)^2} + {b^2}{(Cg)^2} = {({a^2} – {b^2})^2}.$

Standard 11
Mathematics

Similar Questions

Start a Free Trial Now

Confusing about what to choose? Our team will schedule a demo shortly.