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# Two Triangles in a Square

Given that $ABCD$ is a square, $M$ is the mid point of $AD$ and $PC$ is perpendicular to $MB$, prove $DP = DC$.

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Age 14 to 16

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Given that $ABCD$ is a square, $M$ is the mid point of $AD$ and $PC$ is perpendicular to $MB$, prove $DP = DC$.

The largest square which fits into a circle is ABCD and EFGH is a square with G and H on the line CD and E and F on the circumference of the circle. Show that AB = 5EF. Similarly the largest equilateral triangle which fits into a circle is LMN and PQR is an equilateral triangle with P and Q on the line LM and R on the circumference of the circle. Show that LM = 3PQ

You are only given the three midpoints of the sides of a triangle. How can you construct the original triangle?