- Home
- Standard 11
- Mathematics
दीर्घवृत्त में नाभियों और शीर्षों के निर्देशांक, दीर्घ और लघु अक्ष की लंबाइयाँ, उत्केंद्रता तथा नाभिलंब जीवा की लंबाई ज्ञात कीजिए
$36 x^{2}+4 y^{2}=144$
Solution
The given equation is $36 x^{2}+4 y^{2}=144$
It can be written as
$36 x^{2}+4 y^{2}=114$
Or , $\frac{ x ^{2}}{4}+\frac{y^{2}}{36}=1$
Or, $\frac{x^{2}}{2^{2}}+\frac{y^{2}}{6^{2}}=1$ …….. $(1)$
Here, the denominator of $\frac{y^{2}}{6^{2}}$ is greater than the denominator of $\frac{x^{2}}{2^{2}}$
Therefore, the major axis is along the $y-$ axis, while the minor axis is along the $x-$ axis.
On comparing equation $(1)$ with $\frac{ x ^{2}}{b^{2}}+\frac{y^{2}}{a^{2}}=1,$ we obtain $b =2$ and $a =6$
$\therefore c=\sqrt{a^{2}-b^{2}}=\sqrt{36-4}=\sqrt{32}=4 \sqrt{2}$
Therefore,
The coordinates of the foci are $(0, \,\pm 4 \sqrt{2})$
The coordinates of the vertices are $(0,\,±6)$
Length of major axis $=2 a=12$
Length of minor axis $=2 b=4$
Eccentricity, $e=\frac{c}{a}=\frac{4 \sqrt{2}}{6}=\frac{2 \sqrt{2}}{3}$
Length of latus rectum $=\frac{2 b^{2}}{a}=\frac{2 \times 4}{6}=\frac{4}{3}$