Sum of Squares of Sine and Cosine

Theorem
$$\cos^2 x + \sin^2 x = 1$$

Proof
We start from the algebraic definitions of sine and cosine:


 * $$\sin x = $$
 * $$\cos x = $$

From Angle Addition and Subtraction Formulas‎, we have:

$$\cos \left({x - x}\right)$$

$$ $$ $$ $$ $$