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# Law of cosines and law of sines

7 videos
4 skills
The primary tool that we've had to find the length of a side of a triangle given the other two sides has been the Pythagorean theorem, but that only applies to right triangles. In this tutorial, we'll extend this triangle-side-length toolkit with the law of cosines and the law of sines. Using these tool, given information about side lengths and angles, we can figure out things about even non-right triangles that you may have thought weren't even possible!

### Law of cosines

VIDEO 4:38 minutes

### Law of cosines to determine grade

VIDEO 6:41 minutes

### Law of cosines for star distance

VIDEO 6:00 minutes

### Law of cosines

PRACTICE PROBLEMS
Solve missing triangle measures using the law of cosines

### Law of sines

VIDEO 5:58 minutes

### Law of sines for missing angle

VIDEO 5:34 minutes

### Law of sines

PRACTICE PROBLEMS
Solve missing triangle measures using the law of sines

### Law of sines and law of cosines word problems

PRACTICE PROBLEMS

### Proof of the law of cosines

VIDEO 9:26 minutes
Proof of the law of cosines to solve for a side of a triangle when 2 sides and an angle are known.

### Proof: Law of sines

VIDEO 6:32 minutes
A simple proof of the Law of Sines

### Non-right triangle proofs

PRACTICE PROBLEMS