Primitive of Square of Secant Function

Theorem

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

where $C$ is an arbitrary constant.

Proof
From Derivative of Tangent Function:
 * $\dfrac{\mathrm d}{\mathrm dx} \tan \left({x}\right) = \sec^2 \left({x}\right)$

The result follows from the definition of primitive.