Mathematical Similarity Summary

Figures are mathematically similar when…

• corresponding angles are congruent
• there is a scale factor (SF) going both ways
• cross products are equivalent
• area changes by SF squared
• perimeter changes by SF

Any two rectangles are similar. This statement is false, all similar figures follow the reasons listed above.

Any two equilateral triangles ar similar. This statement is true because corresponding angles are congruent.