A triangle is a polygon. It is a closed 3-sided shape made up of straight lines. The ‘tri-’ part of the word triangle means three. A triangle has 3 sides and 3 angles. Interior angles are the angles ...

Use a ruler, protractor and a pair of compasses to construct a triangle accurately. After the triangle has been constructed, leave the construction lines visible so each stage of the process is shown ...

https://doi.org/10.4169/amer.math.monthly.124.1.70 https://www.jstor.org/stable/10.4169/amer.math.monthly.124.1.70 We provide a geometric explanation, based on ...