To understand congruence and similarity, a good understanding of the properties of polygons, including triangles and quadrilaterals, can be helpful. Triangles ABC and GHI are congruent.

These two shapes are similar as they are both rectangles but one is an enlargement of the other. Two triangles are similar if the angles are the same size or the corresponding sides are in the ...

Sketch 1 is intended to help the students attend to the similarities and differences between the three triangles. While initially very similar looking, these triangles behave very differently under ...