1. NOTES
Law of Cosines

2. Who's Law Is It, Anyway? Murphy's Law: Cole's Law ??
Anything that can possibly go wrong, will go wrong (at the worst possible moment).
Cole's Law ??
Finely chopped cabbage

3. Solving an SAS Triangle
The Law of Sines was good for
ASA - two angles and the included side
AAS - two angles and any side
SSA - two sides and an opposite angle (being aware of possible ambiguity)
Why would the Law of Sines not work for an SAS triangle? 15
No side opposite from any angle to get the ratio
26°
12.5

4. Law of Cosines

5. Applying the Cosine Law
Now use it to solve the triangle we started with
Label sides and angles
Side c first C 15
26°
12.5
A B c

6. Applying the Cosine Law
Now calculate the angles
use and solve for B C 15
26°
12.5
A B
c = 6.65

7. Applying the Cosine Law
The remaining angle determined by subtraction
180 – – 26 = 60.25 C 15
26°
12.5
A B
c = 6.65
Experiment with Cosine Law Spreadsheet