$$

a^2+b^2=c^2 \implies \frac{a^2 + b^2}{c^2} = \left( \frac{a}{c} \right)^2 + \left( \frac{b}{c} \right)^2 = 1 \\

\implies \cos^2 \theta + \sin^2 \theta = 1.

$$

Viewed 95

$$

a^2+b^2=c^2 \implies \frac{a^2 + b^2}{c^2} = \left( \frac{a}{c} \right)^2 + \left( \frac{b}{c} \right)^2 = 1 \\

\implies \cos^2 \theta + \sin^2 \theta = 1.

$$