Inside a square with a side length of 10, two congruent equilateral triangles are drawn such that they share one side and each has one vertex on a vertex of the square. What is the side length of the largest square that can be inscribed in the space inside the square and outside of the triangles?
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Triangle height: h = √50
Triangle side: a = h / cos(30º)
Side of a small square: s = a * sin(15º)