As we’ve observed in class, in order to use the Law of Sines, you must know (or be able to find easily) an opposite angle-side pair in the triangle. But what if all you have is two sides and an angle? Is there anything we can do with that? Enter the Law of Cosines, a generalization of the Pythagorean Theorem to non-right triangles.

Also, don’t forget about your poster project, due next Tuesday!

## Today’s links

- Homework: HW 7.9 – Introducing Law of Cosines
- Notes
- Lesson Video 1 (Law of Cosines with SAS triangle)
- Lesson Video 2 (Law of Cosines with SSS triangle)