(1) It is necessary to recite the formula. When learning mathematics, it is best to memorize and understand relevant formulas by doing problems.

(2) For the congruent triangles problem, the key is to label all known conditions. If the figure is complicated, you can draw two triangles to prove on the grade paper.

(3) To know how to push back, for example, if two angles are known to be equal, we must try our best to find an equal corresponding edge.

Congruent triangles refers to two congruent triangles whose three sides and three angles correspond to each other. Congruent triangles is a kind of congruence in geometry. According to congruence transformation, two congruent triangles can be translated, rotated, axisymmetrical, parallel or overlapped. Two triangles are congruent triangles when their corresponding sides and angles are completely opposite.

Congruent triangles can be determined by the following definitions:

SSS (Edge-Edge-Edge): If the three sides of each triangle are equal in length, then the two triangles are congruent triangles.

SAS (Edge-Angle-Edge): If the two sides of each triangle are equal in length and the included angles of the two sides (that is, the angles formed by the two sides) are equal, then the two triangles are congruent triangles.

ASA(Angle-Side-Angle): If the two angles of each triangle are equal, and the sides of the two angles (that is, the common sides) are equal, then the two triangles are congruent triangles.

AAS(Angle-Angle-Side): If the two angles of each triangle are equal, and the opposite side (other than the two sides of the triangle) or the adjacent side (one side of the triangle) of one angle is equal, then the two triangles are congruent triangles.

HL (hypotenuse-leg): One hypotenuse and one right-angled side in a right triangle are equal, and the two triangles are congruent triangles.