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tmua.me Extreme Set C Paper 2 · Q10

Paper 2ProbabilityGeometry

A point PP is chosen at random inside an equilateral triangle ABCABC of side length 22. The probability that PP lies in a region is proportional to that region's area.

Let d1,d2,d3d_1,d_2,d_3 be the perpendicular distances from PP to the lines ABAB, BCBC and CACA, respectively.

Given that d1≥3/2d_1\geq\sqrt3/2, what is the probability that

d12+d22+d32≤32 ?d_1^2+d_2^2+d_3^2\leq\frac32\,?
Aπ93−112\dfrac{\pi}{9\sqrt3}-\dfrac1{12}
B2π93−16\dfrac{2\pi}{9\sqrt3}-\dfrac16
C4π93−13\dfrac{4\pi}{9\sqrt3}-\dfrac13
Dπ33\dfrac{\pi}{3\sqrt3}
E4π93\dfrac{4\pi}{9\sqrt3}
F4π93−16\dfrac{4\pi}{9\sqrt3}-\dfrac16

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