What are the theorems of triangles

What are the theorems of triangles

The center of gravity, the outer center, the perpendicular center, the inner center and the lateral center of an angle are called the five centers of a triangle. The triangle five center theorem is the general term of the triangle center of gravity theorem, the outer center theorem, the perpendicular center theorem, the inner center theorem and the lateral center theorem

How to prove the judgement theorem of parallel line

First of all, straighten out the axioms and theorems that may be used in the determination of parallel lines. Axioms: two straight lines are cut by the third straight line, if the same angle is equal, then the two lines are parallel. (that is: the same angle is equal, and the two lines are parallel) theorem: 1. Two straight lines are cut by the third straight line, if the internal angle is equal, then

What theorem is the basis for making parallel lines of a straight line?
Are two lines parallel at the same angle, equal at the same angle, complementary at the same angle or a / / B, B / / C then a / / C?

When drawing with ruler and triangle board, when the ruler passes through a known point, it will be fixed and unable to move. Push the triangle board to draw parallel lines. In this process, there is an angle that is always equal, that is, the angle between the side of triangle board sticking to a known line and the ruler. So the basis is that the same angle is equal and two lines are parallel