Primitive of Reciprocal of Root of x squared plus a squared/Examples/16 + 9 x^2

Example of Use of Primitive of $\dfrac 1 {\sqrt {x^2 + a^2} }$

 * $\ds \int \dfrac 1 {\sqrt {16 + 9 x^2} } = \dfrac 1 3 \map \ln {3 x + \sqrt {9 x^2 + 16} }$

Proof
We have from Primitive of $\dfrac 1 {\sqrt {x^2 + a^2} }$:

Let $y = 3 x$.

Then: