Students should master the general rules and common methods of auxiliary lines flexibly, which is of great help to improve students' ability to analyze and solve problems. Difficult topics often hide some conditions, so if we want to be able to extend, then the extension here needs the usual accumulation. Usually, the basic knowledge points in class are well mastered, and some special graphics that are usually trained should be memorized.

Junior high school geometry problem solving method proves that two line segments are equal.

1. The corresponding edges in two congruent triangles are equal.

2. Equiangles and equilateral sides of the same triangle.

3. The bisector of the vertex or the high bisector of the bottom of the isosceles triangle. 4. The opposite sides or diagonals of a parallelogram are equal to two line segments separated by intersection points.

5. The midpoint of the hypotenuse of a right triangle is equal to the distance between the three vertices.

Prove that two angles are equal.

1. The angles corresponding to two congruent triangles are equal.

2. Equiangular corners of the same triangle.

3. In an isosceles triangle, the center line (or height) of the base bisects the vertex angle.

4. The isosceles angle, internal dislocation angle or diagonal of the parallelogram of two parallel lines are equal.

5. The complementary angle (or complementary angle) of the same angle (or equal angle) is equal.

Prove that two straight lines are parallel

1. Lines perpendicular to the same line are parallel.

2. The congruent angles are equal, and the internal angle is equal to or parallel to two lines with complementary internal angles.

3. The opposite sides of a parallelogram are parallel.

The center line of triangle is parallel to the third side.

5. The center line of the trapezoid is parallel to the two bottom sides.