A method of finding the area of these figures is a special case of Bramagupta's formula, and relies on finding the difference between each side and the semiperimeter; this is Heron's Formula.
The distances between an arbitrary point to one of these figures sides and vertices is given by the Erdos-Mordell inequality. The relationship between the sides of one of them cut by a segment is given by Stewart's Theorem. A particular condition for collinearity in these figures is called Menelaus' Theorem, which is the dual of Ceva's Theorem. A method of finding the area of these figures is a special case of Bramagupta's formula, and relies on finding the difference between each side and the semiperimeter; this is Heron's Formula. Also containing the incenter, circumcenter, and orthocenter, FTP, name these polygons whose area can be found by the formula ½ times b times h.
The distances between an arbitrary point to one of these figures sides and vertices is given by the Erdos-Mordell inequality.
{Triangle} (Accept {3-gon} or {Trigon})