Lean on me

Two squares and two diagonals. Prove that the angles α and β are equal.

Scroll down for a solution to this problem.


Solution by Matthew Arcus.

Reflection in dashed line and rotation about black point respectively map α and β onto red angle.


Lean on me
We all have pain
We all have sorrow
When you’re not strong
And I’ll be your friend
I’ll help you carry on
You just call on me
Brother when you need a hand
We all need somebody to lean on.
(Song from Bill Withers, 1973)

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