Use identities to simplify the expression

Sec^2x/tanx-tanx

To simplify the expression, we will use the identity:

sec^2(x) = 1 + tan^2(x)

Using the identity, we can rewrite the expression as:
(sec^2(x))/(tan(x) - tan(x))

Since tan(x) - tan(x) is equal to zero, the expression simplifies to:
(sec^2(x))/0

However, division by zero is undefined. Therefore, the expression cannot be further simplified and is undefined.