Find the length of the minor axis of the ellipse 4x2 + 9y2 = 144 ?

  1. 12
  2. 8
  3. 10
  4. None of these

Answer (Detailed Solution Below)

Option 2 : 8
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Detailed Solution

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CONCEPT:

The following are the properties of a horizontal ellipse  where 0 < b < a:

  • Its centre is (0, 0)
  • Its vertices are (- a, 0) and (a, 0)
  • Its foci are (- ae, 0) and (ae, 0)
  • Length of the major axis is 2a
  • Length of the minor axis is 2b
  • Equation of major axis is y = 0
  • Equation of minor axis is x = 0
  • Length of the latus rectum is given by 
  • Eccentricity is given by 

CALCULATION:

Given: Equation of ellipse is 4x2 + 9y2 = 144

The given equation of ellipse can be re-written as 

As we can see that, the given ellipse is a horizontal ellipse.

So, by comparing the given equation of an ellipse with  we get,

⇒ a2 = 36 and b2 = 16

⇒ b = 4

As we know, the length of the minor axis of an ellipse is given by 2b

So, the length of the minor axis is 2 ×  4 = 8 units

Hence, option B is the correct answer.

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