GNA University B.Tech Admissions 2025
100% Placement Assistance | Avail Merit Scholarships | Highest CTC 43 LPA
Length of Latusrectum is considered one of the most asked concept.
46 Questions around this concept.
Consider an ellipse, whose centre is at the origin and its major axis is along the $x$-axis. If its eccentricity is $\frac{3}{5}$ and the distance between its foci is 6 , then the area (in sq. units) of the quadrilateral inscribed in the ellipse, with the vertices as the end points of major and minor axes of ellipse, is
If O is the origin and OB is the semi-minor axis of an ellipse, F1 and F2 are its foci and the angle between F1B and F2B is a right angle, then the square of the eccentricity of the ellipse is
Let $S$ and $S^{\prime}$ be the foci of an ellipse and $B$ be any one of the extremities of its minor axis. If $\Delta S^{\prime} B S$ is a right angled triangle with right angle at B and area $\left(\Delta S^{\prime} B S\right)=8 S q$. units, then the length of a latus rectum of the ellipse is :
JEE Main 2026: Preparation Tips & Study Plan | Previous 10 Year Questions
JEE Main 2025 Most Scoring Concept: January Session | April Session
New: Still looking for BTech admission? Get experts help to choose right college
Don't Miss: Best Public Engineering Colleges
If the latus rectum of the ellipse $\mathrm{x}^2 \tan ^2 \alpha+\mathrm{y}^2 \sec ^2 \alpha=1$ is $\frac{1}{2}$, then $\alpha\left(0<\alpha<\frac{\pi}{3}\right)$ is equal to:
In an ellipse the distance between its foci is and its minor axis is
. Then its eccentricity is
The distance of the point on the ellipse
from a focus is
$
\text { What is the length of the latus rectum of the ellipse: } 9 x^2+25 y^2=225
$
100% Placement Assistance | Avail Merit Scholarships | Highest CTC 43 LPA
Ranked #42 among Engineering colleges in India by NIRF | Highest Package 1.3 CR , 100% Placements | Last Date to Apply: 31st August | Admissions Closing Soon
The length of the latus rectum of the ellipse 3x2 + y2 = 12 is
If the latus rectum of an ellipse is equal to half the minor axis then its eccentricity is equal to
Length of Latus rectum
Let Latus rectum $\mathrm{LL}^{\prime}=2 \alpha$
$\mathrm{S}(\mathrm{ae}, 0)$ is focus, then $\mathrm{LS}=\mathrm{SL}^{\prime}=\alpha$
Coordinates of L and $\mathrm{L}^{\prime}$ become ( $\mathrm{ae}, \alpha$ ) and (ae, $-\alpha$ ) respectively
Equation of ellipse, $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$
Put $x=a e, y=\alpha$ we get, $\frac{(\mathrm{ae})^2}{\mathrm{a}^2}+\frac{\alpha^2}{\mathrm{~b}^2}=1 \Rightarrow \alpha^2=\mathrm{b}^2\left(1-\mathrm{e}^2\right)$
$
\begin{aligned}
& \alpha^2=\mathrm{b}^2\left(\frac{\mathrm{~b}^2}{\mathrm{a}^2}\right) \quad\left[\mathrm{b}^2=\mathrm{a}^2\left(1-\mathrm{e}^2\right)\right] \\
& \alpha=\frac{\mathrm{b}^2}{\mathrm{a}} \\
& \Rightarrow 2 \alpha=\mathrm{LL}^{\prime}=\frac{2 \mathrm{~b}^2}{\mathrm{a}}
\end{aligned}
$
End Points of Latus rectum
$\mathrm{L}=\left(\mathrm{ae}, \frac{\mathrm{v}}{\mathrm{a}}\right)$ and $\mathrm{L}^{\prime}=\left(\mathrm{ae},-\frac{\mathrm{v}}{\mathrm{a}}\right)$
Focal Distance of a Point:
The sum of the focal distance of any point on the ellipse is equal to the major axis.
Let $\mathrm{P}(\mathrm{x}, \mathrm{y})$ be any point on the ellipse.
Here, $\quad \begin{aligned} & S P=e P M=e\left(\frac{a}{e}-x\right)=a-e x \\ & \\ & S^{\prime} P=e P M^{\prime}=e\left(\frac{a}{e}+x\right)=a+e x\end{aligned}$
Now, $\mathrm{SP}+\mathrm{S}^{\prime} \mathrm{P}=\mathrm{a}-\mathrm{ex}+\mathrm{a}+\mathrm{ex}=2 \mathrm{a}=\mathrm{AA}^{\prime}=$ constant.
Thus the sum of the focal distances of a point on the ellipse is constant.
"Stay in the loop. Receive exam news, study resources, and expert advice!"