Primitive of Square of Secant Function

Theorem

 * $\displaystyle \int \sec^2 x \rd x = \tan x + C$

where $C$ is an arbitrary constant.

Proof
From Derivative of Tangent Function:
 * $\dfrac \d {\d x} \map \tan x = \map {\sec^2} x$

The result follows from the definition of primitive.