1. Law of Cosine
Chapter 8.3

2. Law of Sine too, but…… Law of Cosine
If the triangle is not a right triangle, we have 4 case scenarios to consider.
Law of Sine
too, but…… A S S S A A A S A
Case 1: ASA or AAS
Case 2: SSA
Law of Cosine S S S A S S
Case 3: SAS
Case 4: SSS

3. Law of Cosine a² = b² + c² - 2bcCosα b² = a² + c² - 2acCosβ
c² = a² + b² -2abCosγ S S S A S S
Case 3: SAS
Case 4: SSS

4. Solve the triangle. a² = b² + c² - 2bcCosα b² = a² + c² - 2acCosβ
c² = a² + b² -2abCosγ β S c 2 α
60° A 3 S
Side-Angle-Side

5. Solve the triangle. a² = b² + c² - 2bcCosα b² = a² + c² - 2acCosβ
c² = a² + b² -2abCosγ γ S 2 b
45° α A 4 S
Side-Angle-Side

6. Solve the triangle. a² = b² + c² - 2bcCosα b² = a² + c² - 2acCosβ
c² = a² + b² -2abCosγ γ S S 4 3 β α 6 S
Side-Side-Side

7. Solve the triangle. a² = b² + c² - 2bcCosα b² = a² + c² - 2acCosβ
c² = a² + b² -2abCosγ γ S S 9 6 β α 4 S
Side-Side-Side