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Let an ellipse with centre 1, 0 and latus rectum of length 12 have its major axis along x-axis. If its minor axis subtends an angle 60 at the foci, then the square of the sum of the lengths of its minor and major axes is equal to _______.
MathematicsEllipseJEE MainJEE Main 2023 (15 Apr Shift 1)
Solution:
2187 Upvotes Verified Answer
The correct answer is: 9

Given,

An ellipse with centre 1, 0 and latus rectum of length 12 have its major axis along x-axis 

And its minor axis subtends an angle 60 at the foci, 

So, on plotting the diagram we get,

Now from diagram we get,

2b2a=12b2=a4 ...1

And  tan30=bae

132=bae2

13=b2a2-b2

a2-b2=3b2

b2=a24  .......2

Now from equation 1 & 2 we get,

a=1, b2=14b=12

Hence, 2a+2b2=9

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