Answer:
(cosx + 2)(cosx - 1)
Step-by-step explanation:
Using the trigonometric identity
cos²x + sin²x = 1 ⇒ sin²x = 1 - cos²x
Given
cosx - sin²x - 1
= cosx - (1 - cos²x) - 1
= cosx - 1 + cos²x - 1
= cos²x + cosx - 2
= (cosx + 2)(cosx - 1) ← in factored form