$${ \cos }^{ 2 } \theta - { \tan }^{ 2 } \theta =$$
$\left(\cos(\theta )\right)^{2}-\left(\tan(\theta )\right)^{2}$
$\frac{\left(\left(\cos(\theta )\right)^{2}-\sin(\theta )\right)\left(\left(\cos(\theta )\right)^{2}+\sin(\theta )\right)}{\left(\cos(\theta )\right)^{2}}$
