7. Find the coordinates of the foci, the vertices, the length of major axis, the minor axis, the eccentricity and the length of the latus rectum of the ellipse.

       36x^2 + 4y^2 =144

Answers (1)

Given

The equation of the ellipse

36x^2 + 4y^2 =144

\Rightarrow \frac{36}{144}x^2 + \frac{4}{144}y^2 =1

\Rightarrow \frac{1}{4}x^2 + \frac{1}{36}y^2 =1

\frac{x^2}{2^2} + \frac{y^2}{6^2} = 1

As we can see from the equation, the major axis is along Y-axis and the minor axis is along X-axis.

On comparing the given equation with the standard equation of such  ellipse, which is 

\frac{x^2}{b^2} + \frac{y^2}{a^2} = 1

We get 

a=6 and b=2.

So,

c=\sqrt{a^2-b^2}=\sqrt{6^2-2^2}

c=\sqrt{32}=4\sqrt{2}

Hence,

Coordinates of the foci:  

(0,c)\:and\:(0,-c)=(0,4\sqrt{2})\:and\:(0,-4\sqrt{2})

The vertices:

(0,a)\:and\:(0,-a)=(0,6)\:and\:(0,-6)

The length of the major axis:

2a=2(6)=12

The length of minor axis:

2b=2(2)=4

The eccentricity :

e=\frac{c}{a}=\frac{4\sqrt{2}}{6}=\frac{2\sqrt{2}}{3}

The length of the latus rectum:

\frac{2b^2}{a}=\frac{2(2)^2}{6}=\frac{8}{6}=\frac{4}{3}

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