Answer
$-3\sqrt 2+3i\sqrt 2$
Work Step by Step
$6$ cis $135^{\circ}$=$6(\cos135^{\circ}+i\sin135^{\circ})$
It is known that $\cos135^{\circ}=-\frac{\sqrt 2}{2}$ and $\sin135^{\circ}=\frac{\sqrt 2}{2}$
Substituting these values in the expression and solving:
$6(\cos135^{\circ}+i\sin135^{\circ})=6(-\frac{\sqrt 2}{2}+\frac{\sqrt 2}{2}i)=-3\sqrt 2+3i\sqrt 2$
