Junior high school mathematics, geometric triangle three lines in one, do you know what conditions can prove the other part? Thank you very much ! !
Three-in-one can be used directly, such as isosceles right triangle. You see AB=BC, that is, B is the midpoint of the bottom AC. If the vertex of this equilateral triangle is D, then you can directly use BD⊥AC in the geometric problem that BD is the bisector of angular ADC without proof.