#triangle sides
- Antiparallel line — A straight line that intersects the sides of a given angle in such a way that it forms with them an inverted triangle relative to the symmetry of a classic parallel line. This structural arrangement causes the angle formed by the antiparallel with one side to be perfectly equal to the angle formed by the base line with the other side, having important applications in the study of the antiparallel lines theorem in a triangle.