A Proof that the Vertex Angle Sum of a Pentagram is 180 degrees

The pentagram is a five-pointed star. It was used by the ancient Greeks as a symbol of faith.  In this post, we exhibit the mathematics of pentagrams — we show that the sum of the angle measures of its vertices equals 180°. For regular pentagrams, the proof is simple. By the inscribed angle theorem, the measure of an inscribed angle … Continue reading A Proof that the Vertex Angle Sum of a Pentagram is 180 degrees