# Who loves geometric inequality?

Geometry Level 3

Let S be a square of unit area, consider any quadrilateral which has one vertex on each side of S. If $$a, b, c$$ and $$d$$ denote the length of sides of the quadrilateral. Find the minimum value of $$a^2+b^2+c^2+d^2$$

Special Credit : Find the maximum value too.

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