For questions about properties and applications of triangles.

A triangle is a polygon with three sides. It is an important geometric figure, because any polygon can be subdivided into triangles.

Triangles can be classified by the number of sides they have that have equal length

- All three sides of an
*equilateral*triangle have equal length. - An
*isosceles*triangle has at least two sides of equal length. - A
*scalene*triangle is a triangle that is not isosceles, that is, it has no sides with equal length.

A triangle may also be classified by describing its angles. A triangle is said to be a *right triangle* if it contains a right angle, and *obtuse triangle* if it contains an obtuse angle, or an *acute triangle* if all three of its angles are acute.