As shown above, two identical ellipses are arranged in an equilateral triangle. There exists the unique value of eccentricity , such that:
Input as your answer.
This problem is inspired by the comment (under Pi Han Goh 's solution) from the other problem I posted.
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Let the x -axis be the base of the triangle. Then the horizontal ellipse will have equation a 2 x 2 + b 2 ( y − b ) 2 = 1 and this will be tangential to the slant lines y = 2 a ± x 3 A standard result, effectively derived by @Pi Han Goh , states that a line y = m x + c will be tangential to the ellipse a 2 x 2 + b 2 y 2 = 1 provided that a 2 m 2 + b 2 = c 2 . In this case, we deduce that 3 a 2 + b 2 = ( 2 a − b ) 2 and hence that a = 4 b , which makes the eccentricity of the ellipse equal to e = 4 1 1 5 , giving ⌊ 1 0 6 e ⌋ = 9 6 8 2 4 5 .