19.3 Pythagorean identities
Pythagorean identities
Pythagorean identities are formulas, derived from Pythagorean Theorem, that allow us to find out where a point is on the unit circle. Learn the tricks and tips on how to use the unit circle to derive and prove the Pythagorean identities can be difficult.
Basic concepts:
 Using sine ratio to calculate angles and side (Sin = $\frac{o}{h})$
 Using cosine ratio to calculate angles and side (Cos = $\frac{a}{h}$)
 Factoring difference of squares: $x^2  y^2$
 Unit circle
Related concepts:
 Solving trigonometric equations using pythagorean identities
Lessons
Notes:
Download the Trigonometry identities chart here

2.
Simplify expressions:

3.
Prove identities