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 […]
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Geonext Tutorial 1 – Constructing an Equilateral Triangle

Geonext is aJava-written interactive and free geometry software. It is developed by the Lehrstuhl für Mathematik und ihre Didaktik (Chair of mathematics and its didactics) of the University of Bayreuth in Germany and released under the GNU General Public License. 1.) Click the New Board button. 2.) To draw a circle with center A and passing through B, click […]
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