GED Math Practice Test

For two triangles to be similar, their corresponding angles must be equal. This relationship is fundamental to the concept of similarity in geometry. When the angles of two triangles are equal, it indicates that their shapes are identical, even if their sizes may differ. This means that the triangles can be scaled versions of one another.

The proportionality of sides comes into play as well, but it is the equality of the corresponding angles that truly defines the similarity. Once this angle equality is established, it follows that the lengths of the sides must be proportional, which is another way of expressing the similarity. So, in the context of defining triangle similarity, the equality of corresponding angles is the essential criterion.