Final answer:
The equation sec² x - 1 = tan² x is an identity that can be proven using trigonometric identities.
Step-by-step explanation:
The equation sec² x - 1 = tan² x is an identity.
To prove this, we can use the trigonometric identities:
sec² x = 1 + tan² x and 1 = sin² x + cos² x.
Substituting these identities into the original equation, we get:
1 + tan² x - 1 = tan² x
tan² x = tan² x
Since the equation is true for all values of x, it is an identity.