This large, nearly equilateral triangle is composed of ... form the base of the inverted Triangle. The Pollux-Mars and Castor-Mars sides of the Triangle measure about 7 degrees in length, while ...

Henry Dudeney, a self-taught English mathematician and puzzle columnist, asked his readers to dissect an equilateral triangle into the smallest number of pieces that could be rearranged into a square.

The interior angles in a triangle always add up to 180º. An equilateral triangle has 3 sides of equal length. The dashes on the lines show they are equal in length. All of the angles are also equal.