1. Tangent = Sine / Cosine

​

2. The Law of Cosines becomes the Pythagorean theorem when the angle is fixed at 90 degrees (𝜋/2 in radians) because cos 90 deg = 0, thus cancelling the whole term.

​

3. We can take the trigonometric identity we are given, and first, divide every term in it by cos^2(theta), and then second, divide every term in it by sin^2(theta).

​

​