what is the definition of triangle in math
Triangle A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted   △ A B C  {\displaystyle \triangle ABC} .
Circle As proved by Archimedes, in his Measurement of a Circle, the area enclosed by a circle is equal to that of a triangle whose base has the length of the circle's circumference and whose height equals the circle's radius,[7] which comes to Ï€ multiplied by the radius squared:
Pi Ï€ is commonly defined as the ratio of a circle's circumference C to its diameter d:[9]
Heptagon In geometry, a heptagon is a seven-sided polygon or 7-gon.
The Pale The word pale derives ultimately from the Latin word
Decagon In geometry, a decagon is a ten-sided polygon or 10-gon.[1]