解决比例线段的问题,先要准确掌握有关比例线段的五条主要定理:平行线分线段成比例定理、三角形内(外)角平分线性质定理、相似三角形的判定和性质定理、射影定理、圆幂定理。它们是解决此类问题的有力工具和重要的理论依据。 其次,要勤于思索,重于分析,严于推理, To solve the problem of proportional line segments, we must first accurately grasp the five main theorems of proportional line segments: the proportional theorem of parallel line segments, the bisection (external) angle bisector property theorem of triangles, the determination and property theorem of similar triangles, the projective theorem, and the circular power theorem. They are powerful tools and important theoretical basis for solving such problems. Second, we must be diligent in thinking, stress analysis, and be strict with reasoning.