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Area below envelope of strange lines

1925SpecialistCalculusCoordinate Geometry

Harvard-MIT Mathematics Tournament

A line in the plane is called strange if it passes through $(a, 0)$ and $(0, 10-a)$ for some $a$ in the interval $[0, 10]$. A point in the plane is called charming if it lies in the first quadrant and also lies below some strange line. What is the area of the set of all charming points?
0 students attempted0% solvedRating 1925

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