Determine if True cos(theta)^2+sin(theta)^2=1

$\cos^{2} (θ) + \sin^{2} (θ) = 1$

Start on the left side.

$\cos^{2} (θ) + \sin^{2} (θ)$

Apply Pythagorean identity.

Rearrange terms.

$\sin^{2} (θ) + \cos^{2} (θ)$

Apply pythagorean identity.

$1$

Because the two sides have been shown to be equivalent, the equation is an identity.

$\cos^{2} (θ) + \sin^{2} (θ) = 1$ is an identity