Write the Word or Phrase That Best Completes Each Statement $$\cot x \sec ^ { 4 } x = \cot x + 2 \tan x + \tan ^ { 3 } x$$

Essay

Write the word or phrase that best completes each statement or answers the question.
Establish the identity.
- $$\cot x \sec ^ { 4 } x = \cot x + 2 \tan x + \tan ^ { 3 } x$$