Stage: 4 Challenge Level: 
Given that $ABCD$ is a square, $M$ is the mid point of $AD$ and $PC$ is perpendicular to $MB$, prove $DP = DC$.
Scale factors. Reflections. Rotations. Squares. Similarity. Asymptotes. Congruence. Isosceles triangles. Symmetry. Graph sketching.
Published May 1998.
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