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Question -

Find the equation of the hyperbola, referred to its principal axes as axes of coordinates, in the following cases:
(i) the distance between the foci = 16 and eccentricity = √2
(ii) conjugate axis is 5 and the distance between foci = 13
(iii) conjugate axis is 7 and passes through the point (3, -2)



Answer -

(i) the distance between the foci = 16 and eccentricity =√2

Given:

Distance between the foci = 16

Eccentricity = √2

Let us compare with the equation of the form

Distance between the foci is 2ae and b2 = a2(e2 –1)

So,

2ae = 16

ae = 16/2

a√2 = 8

a = 8/√2

a2 = 64/2

= 32

We know that, b2 = a2(e2 –1)

So, b2 = 32 [(√2)2 – 1]

= 32 (2 – 1)

= 32

The Equation of hyperbola is given as

x2 – y2 = 32

The Equation of hyperbola is x2 – y2 =32

(ii) conjugate axis is 5 and the distance between foci = 13

Given:

Conjugate axis = 5

Distance between foci = 13

Let us compare with the equation of the form

Distance between the foci is 2ae and b2 = a2(e2 –1)

Length of conjugate axis is 2b

So,

2b = 5

b = 5/2

b2 = 25/4

We know that, 2ae = 13

ae = 13/2

a2e2 = 169/4

b2 = a2(e2 – 1)

b2 = a2e2 – a2

25/4 = 169/4 – a2

a2 = 169/4 – 25/4

= 144/4

= 36

The Equation of hyperbola is given as

The Equation of hyperbola is 25x2 – 144y2 =900

(iii) conjugate axis is 7 and passes through the point (3,-2)

Given:

Conjugate axis = 7

Passes through the point (3, -2)

Conjugate axis is 2b

So,

2b = 7

b = 7/2

b2 = 49/4

The Equation of hyperbola is given as

Since it passes through points (3, -2)

The Equation of hyperbola is 65x2 – 36y2 =441

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