Pythagorean Identity. This identity is so named because we can read it off of the unit circle by looking at any of the right triangles and remembering the Pythagorean Theorem.
- Proof of the pythagorean identity (6:12)
- Using the Pythagorean trig identity (6:15)
Given that and that is in the third quadrant, Sal finds .
- Solving problems of the type: given that is in the third quadrant and that , find .