Explanation

The Law of Cosines generalizes the Pythagorean Theorem.

Formula:
c² = a² + b² − 2ab cos(C)

Use when:

• You know SAS

• You know SSS

If C = 90°, the formula becomes:
c² = a² + b²

Quiz

1. What theorem is the Law of Cosines related to?

2. When is the Law of Cosines used?

3. What does cos(C) represent?

4. Can this law find angles?

5. Does it work for right triangles?

Answer Key

1. Pythagorean Theorem

2. SAS or SSS

3. The included angle

4. Yes

5. Yes