Evaluate tan(theta)^2-sec(theta)^2

$\tan^{2} (θ) - \sec^{2} (θ)$

Simplify with factoring out.

Reorder $\tan^{2} (θ)$ and $- \sec^{2} (θ)$ .

$- \sec^{2} (θ) + \tan^{2} (θ)$

Factor $- 1$ out of $- \sec^{2} (θ)$ .

$- (\sec^{2} (θ)) + \tan^{2} (θ)$

Factor $- 1$ out of $\tan^{2} (θ)$ .

$- (\sec^{2} (θ)) - 1 (- \tan^{2} (θ))$

Factor $- 1$ out of $- (\sec^{2} (θ)) - 1 (- \tan^{2} (θ))$ .

$- (\sec^{2} (θ) - \tan^{2} (θ))$

Apply pythagorean identity.

$- 1 \cdot 1$

Multiply $- 1$ by $1$ .

$- 1$