Deriving the Pythagorean Trigonometric Identities

Let's talk about the Pythagorean Trig Identities. Let's talk about how to derive the identities starting with Pythagorean theorem.

Using the Pythagorean theorem, we get:

Since sin(θ)=O/H and cos(θ)=A/H, then we get with some substitution:

Notice when you divide both sides of eqn. 1 by sin²θ.

Also see what happens when you take eqn. 1 and divide both sides by cos²θ.

So this is how you can derive the three Pythagorean Trigonometric Identities including…

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