`int ln\ x\ dx`

Our priorities list above tells us to choose the logarithm expression for `u`. (of course, there's no other choice here. :-)

So with `u=ln\ x`, we have `du=dx/x`.

Then `dv` will simply be `dv=dx` and integrating this gives `v=x`.

Subsituting these into the Integration by Parts formula gives:

`{: (int ln\ x\ dx, =int u\ dv),(,=uv-intv\ du),(,=x\ ln\ x-intx(dx)/x),(,=x\ ln\ x-intdx),(,=x\ ln\ x-x+K) :}`