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Question:

If the area of an equilateral triangle inscribed in the circle x² + y² + 10x + 12y + c = 0 is 27√3 sq. units, then c is equal to:

25

20

13

𕒶5

Solution:

The correct option is B
25
3(1/2r²sin120⁰) = 27√3
r²/2√3 = 27√3
3r² = 108
r² = 36
Radius = √25 + 36 - c = √36
c = 25
∴ Option (2)