# Angles in a Cube I

Let denote the vertices of a cube ABCD (for the bottom face) and A'B'C'D' (for the top face), with A' above A, etc. What is the angle AB'C?

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Copyright © 1996-2017 Alexander Bogomolny### Solution

Add to the picture the side AC. As all three segments AB', B'C and AC are the diagonals of equal squares, they are equal and, thus, form an equalteral triangle, implying that angle AB'C is 60°.

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Copyright © 1996-2017 Alexander Bogomolny61183901 |