Pythagorean trigonometric identity (${\sin }^{2}x+{\cos }^{2}x=1$)

The Pythagorean trigonometric identities are fundamental relationships between the sine and cosine functions that stem from the Pythagorean theorem. They are derived from the fact that for a right triangle with an angle \( \theta \), the following equation holds: \[ \sin^2(\theta) + \cos^2(\theta) = 1 \] This is the most basic Pythagorean identity.