Primitive of Product of Secant and Tangent

Theorem

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

where $C$ is an arbitrary constant.

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

The result follows from the definition of primitive.