Congruence & Similarity

When are two triangles the same?

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• SSS, SAS and ASA guarantee congruence; SSA can give two different triangles.
• Two matching angles (AA) guarantee similarity; similar triangles have proportional sides.
• The altitude to the hypotenuse is the geometric mean of the two pieces.

Steps

1. Enough information
2. The ambiguous case
3. Similar triangles
4. The altitude
5. Measuring a tree
6. Areas of similar triangles