Answer:
[tex] { \cot}^{2} \theta - { \cos }^{2} \theta = { \cot }^{2} \theta { \cos }^{2} \theta \\ divide \: by \: { \cos }^{2} \theta : \\ \frac{1}{ { \sin }^{2}\theta } - 1 = { \cot}^{2} \theta \\ 1 - { \sin }^{2} \theta = { \cos }^{2} \theta \\ identity = > \: { \boxed{ { \sin}^{2} \theta + { \cos}^{2} \theta = 1}}[/tex]
