1. Demana, Waits, Foley, Kennedy
5.6
The Law of Cosines

2. What you’ll learn about
Deriving the Law of Cosines
Solving Triangles (SAS, SSS)
Triangle Area and Heron’s Formula
Applications
… and why
The Law of Cosines is an important extension of the
Pythagorean theorem, with many applications.

3. Law of Cosines
Pythag thrm-ish
Angle & Side opp are at the ends

4. Example: Solving a Triangle (SAS)

5. Solution

6. Solution

7. Area of a Triangle
Find the area of a triangle with sides 10, 12, 14.

8. Solution
Find the area of a triangle with sides 10, 12, 14.

9. The figure shown is three mutually tangent circles, with a triangle whose vertices are at the midpoint of each circle.
The radii of circles A, B and C are 6, 8 and 12. What is the area of the shaded region?

10. Homework
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