Primitive of Product of Secant and Tangent

Theorem

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

where $C$ is an arbitrary constant.

Proof
From Derivative of Secant Function:
 * $\dfrac{\mathrm d}{\mathrm dx} \sec x = \sec x \tan x$

The result follows from the definition of primitive.