Construct an equilateral triangle inscribed a given circle

How to Draw an equilateral triangle inscribed in a given circle. easy step-by-step . Positive Happy by PeriTune https://soundcloud.com/sei_peridot Creative Commons — Attribution 3.0 Unported — CC BY 3.0 http://creativecommons.org/licenses/by/3.0/ Music promoted by Audio Library https://youtu.be/TutcA4JPa7Q