Two triangles are similar: the angles of the two triangles are equal and the length of the sides is proportional (the value is set to a), so the area ratio is a? .

Two triangles that can completely overlap are called congruent triangles, and "congruence" is represented by the symbol "",which is pronounced "congruence".

(1) If two angles of a triangle are equal to two angles of another triangle, then the two triangles are similar (abbreviated as two angles are equal and two triangles are similar).

(2) If two sides of a triangle are proportional to two sides of another triangle and the included angle is equal, then two triangles are similar (abbreviated as: two sides are proportional and the included angle is equal, and two triangles are similar).

Extended data:

Similar triangles is one of the important proof models in geometry, and it is a generalization of congruent triangles. Congruent triangles can be understood as similar triangles with a similarity ratio of 1. Similar triangles is actually a set of theorems, which mainly describes the relationship between edges and angles in two triangles in similar triangles geometry.

Definition? The corresponding angles of similar triangles are equal, and the corresponding sides are proportional.

Theorem? The ratio of any corresponding line segment in similar triangles is equal to the similarity ratio.

Theorem? The area ratio of similar triangles is equal to the square of the similarity ratio.

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