第637题：internal angle

A triangle is a closed shape that has three sides (which are line segments) and three vertices (the points where the sides meet). It also has three internal angles, and we already know that the sum of them is always $? \degree$

A line segment is the part of a line that lies between two points, without extending to infinity. We can label line segments from point A to point B as $\overline{AB}$

A point is a specific location in space. Points describe a position, but have no size or shape themselves.

The internal angles of a polygon are the angles on the inside, at every vertex.