There are two ways to construct a triangle using a ruler and a protractor. The first is a Side, Angle, Side (SAS) construction where two sides and the angle between them is known. The second is an ...

Summary We prove the next generalization of the Steiner-Lehmus theorem: if two equal cevians intersect with each other on the angle bisector of the third triangle vertex, then the triangle is ...

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. What is a triangle? We all know that a triangle is a three-sided shape — 1, 2, 3 sides. A triangle also ...