including triangles and quadrilaterals, can be helpful. Triangles ABC and GHI are congruent. Triangle GHI is the same as ABC but has been rotated 90° anticlockwise. Triangle DEF is a different size.

and then congruent triangles (equilateral triangles) form the pitched roof. An easy way to remember congruent angles is to relate the word "congruent" and to how that term is used in reference to ...