Gujarati
Hindi
10-2. Parabola, Ellipse, Hyperbola
normal

Consider an ellipse with foci at $(5,15)$ and $(21,15)$. If the $X$-axis is a tangent to the ellipse, then the length of its major axis equals

A

$17$

B

$34$

C

$13$

D

$\sqrt{416}$

(KVPY-2009)

Solution

(b)

Given, $(5,15)$ and $(21,15)$

are foci of parabola and $X$-axis is tangent of ellipse.

$2 a e =16 \text { and } b=15$

$a e =8 \text { and } b=15$

$a e^2 =a^2-b^2$

$16 =a^2-225$

$a^2 =289$

$a =17$

$\therefore$ Length of major axis $=34$

Standard 11
Mathematics

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