When shape is not enough

Hold up a small bangle and a big one. The shape is the same. Neither fits the other wrist.

Look at each pair. Choose its name.

Corners give the shape, not the size

AAA (angle, angle, angle) is not a test for congruence. Three equal angles give the same shape. They do not tell the size.

Example: two triangles with corners 40°, 60° and 80°. The corners add to 180°: 40 + 60 + 80 = 180. One is small. One is large. They are not congruent.

Sides in one ratio: every side is multiplied by the same number.

Try the lab to finish this lesson.