$\mathrm{A}\mathrm{B}\mathrm{C}$ is a right triangle, right-angled at the vertex $\mathrm{A}.$ A circle is drawn to touch the sides $\mathrm{A}\mathrm{B}$ and $\mathrm{A}\mathrm{C}$ at points $\mathrm{P}$ and $\mathrm{Q}$ respectively such that the other end points of the diameters passing through $\mathrm{P}$ and $\mathrm{Q}$ lie on the side $\mathrm{B}\mathrm{C}.$ If $\mathrm{A}\mathrm{B}=6$ units, then the area (in sq. units) of the circular sector which lies inside the triangle is