Conic Sections (Hyperbola) NCERT Solutions Exercise 10.4 Class 11 Math (Set-1)

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NCERT Question.1 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$\frac{x^2}{16} – \frac{y^2}{9} = 1$$

Solution:
Comparing the given equation with
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

We conclude that the transverse axis is along the x-axis.

Hence,
$$a^2 = 16, \quad b^2 = 9$$

$$a = \pm 4, \quad b = \pm 3$$

Foci:
Foci are $(c, 0)$ and $(-c, 0)$

$$c = \sqrt{a^2 + b^2} = \sqrt{16 + 9} = \sqrt{25} = 5$$
So, the foci are $(5, 0)$ and $(-5, 0)$

Vertices:
Vertices are $(a, 0)$ and $(-a, 0)$

Hence, $(4, 0)$ and $(-4, 0)$

Eccentricity:
$$e = \frac{c}{a} = \frac{5}{4}$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 9}{4} = \frac{9}{2}$$


NCERT Question.2 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$\frac{y^2}{9} – \frac{x^2}{27} = 1$$

Solution:
Comparing the given equation with
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

We conclude that the transverse axis is along the y-axis.

Hence,
$$a^2 = 9, \quad b^2 = 27$$
$$a = \pm 3, \quad b = \pm 3\sqrt{3}$$

Foci:
Foci are $(0, c)$ and $(0, -c)$

$$c = \sqrt{a^2 + b^2} = \sqrt{9 + 27} = \sqrt{36} = 6$$
So, the foci are $(0, 6)$ and $(0, -6)$

Vertices:
Vertices are $(0, a)$ and $(0, -a)$

Hence, $(0, 3)$ and $(0, -3)$

Eccentricity:
$$e = \frac{c}{a} = \frac{6}{3} = 2$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 27}{3} = 18$$


NCERT Question.3 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$9y^2 – 4x^2 = 36$$

Solution:
Dividing both sides by $36$, we get
$$\frac{y^2}{4} – \frac{x^2}{9} = 1$$

Comparing the given equation with
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

We conclude that the transverse axis is along the y-axis.

Hence,
$$a^2 = 4, \quad b^2 = 9$$
$$a = \pm 2, \quad b = \pm 3$$

Foci:
Foci are $(0, c)$ and $(0, -c)$

$$c = \sqrt{a^2 + b^2} = \sqrt{4 + 9} = \sqrt{13}$$
So, the foci are $(0, \sqrt{13})$ and $(0, -\sqrt{13})$

Vertices:
Vertices are $(0, a)$ and $(0, -a)$

Hence, $(0, 2)$ and $(0, -2)$

Eccentricity:
$$e = \frac{c}{a} = \frac{\sqrt{13}}{2}$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 9}{2} = 9$$


NCERT Question 4 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$16x^2 – 9y^2 = 576$$

Solution:
Dividing both sides by $576$, we get
$$\frac{x^2}{36} – \frac{y^2}{64} = 1$$

Comparing the given equation with
$$\frac{x^2}{a^2} – \frac{y^2}{b^2} = 1$$

We conclude that the transverse axis is along the x-axis.

Hence,
$$a^2 = 36, \quad b^2 = 64$$
$$a = \pm 6, \quad b = \pm 8$$

Foci:
Foci are $(c, 0)$ and $(-c, 0)$

$$c = \sqrt{a^2 + b^2} = \sqrt{36 + 64} = \sqrt{100} = 10$$
So, the foci are $(10, 0)$ and $(-10, 0)$

Vertices:
Vertices are $(a, 0)$ and $(-a, 0)$

Hence, $(6, 0)$ and $(-6, 0)$

Eccentricity:
$$e = \frac{c}{a} = \frac{10}{6} = \frac{5}{3}$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 64}{6} = \frac{64}{3}$$


NCERT Question 5 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$5y^2 – 9x^2 = 36$$

Solution:
Dividing both sides by $36$, we get
$$\dfrac{y^2}{\dfrac{36}{5}} – \dfrac{x^2}{4} = 1$$

Comparing with
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

We conclude that the transverse axis is along the y-axis.

Hence,
$$a^2 = \frac{36}{5}, \quad b^2 = 4$$
$$a = \pm \frac{6}{\sqrt{5}}, \quad b = \pm 2$$

Foci:
Foci are $(0, c)$ and $(0, -c)$

$$c = \sqrt{a^2 + b^2} = \sqrt{\frac{36}{5} + 4} = \sqrt{\frac{56}{5}} = \frac{2\sqrt{14}}{\sqrt{5}}$$
So, the foci are $(0, \frac{2\sqrt{14}}{\sqrt{5}})$ and $(0, -\frac{2\sqrt{14}}{\sqrt{5}})$

Vertices:
Vertices are $(0, a)$ and $(0, -a)$

Hence, $(0, \frac{6}{\sqrt{5}})$ and $(0, -\frac{6}{\sqrt{5}})$

Eccentricity:
$$e = \frac{c}{a} = \frac{\frac{2\sqrt{14}}{\sqrt{5}}}{\frac{6}{\sqrt{5}}} = \frac{\sqrt{14}}{3}$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 4}{\frac{6}{\sqrt{5}}} = \frac{4\sqrt{5}}{3}$$


NCERT Question 6 : Find the coordinates of the foci and the vertices, the eccentricity and the length of the latus rectum of the hyperbola
$$49y^2 – 16x^2 = 784$$

Solution:
Dividing both sides by $784$, we get
$$\frac{y^2}{16} – \frac{x^2}{49} = 1$$

Comparing the given equation with
$$\frac{y^2}{a^2} – \frac{x^2}{b^2} = 1$$

We conclude that the transverse axis is along the y-axis.

Hence,
$$a^2 = 16, \quad b^2 = 49$$
$$a = \pm 4, \quad b = \pm 7$$

Foci:
Foci are $(0, c)$ and $(0, -c)$

$$c = \sqrt{a^2 + b^2} = \sqrt{16 + 49} = \sqrt{65}$$
So, the foci are $(0, \sqrt{65})$ and $(0, -\sqrt{65})$

Vertices:
Vertices are $(0, a)$ and $(0, -a)$

Hence, $(0, 4)$ and $(0, -4)$

Eccentricity:
$$e = \frac{c}{a} = \frac{\sqrt{65}}{4}$$

Length of Latus Rectum:
$$= \frac{2b^2}{a} = \frac{2 \times 49}{4} = \frac{49}{2}$$

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โฌ…๏ธ Hyperbola NCERT Solutions Exercise 10.4 Set-2 Ellipse NCERT Solutions Exercise 10.3 โžก๏ธ

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