Similarity is a generalisation of congruence: two similar figures have the same shape but not necessarily the same size. The fundamental case is that of triangles.
Definition — Similar triangles
Two triangles are similar if they have respectively congruent angles and corresponding sides in proportion (ratio of similarity ).
The number is the ratio of similarity: it indicates how many times each side of one triangle is larger than the corresponding side of the other. If the two triangles are congruent.
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Topics: Similarity
Concepts: Ratio of similarity · Similarity · Similar triangles
Skills: Synthetic geometry