Answer
$$ - 3 - 3\sqrt 3 i$$
Work Step by Step
$$\eqalign{
& \left[ {3\operatorname{cis} {{135}^ \circ }} \right]\left[ {2\operatorname{cis} {{105}^ \circ }} \right] \cr
& {\text{Multiply}} \cr
& {\text{ = }}\left( {3 \cdot 2} \right)\operatorname{cis} \left( {{{135}^ \circ } + {{105}^ \circ }} \right) \cr
& {\text{ = }}6\operatorname{cis} \left( {{{240}^ \circ }} \right) \cr
& {\text{Write in the rectangular form}} \cr
& = 6\left( {\cos {{240}^ \circ } + i\sin {{240}^ \circ }} \right) \cr
& = 6\left( { - \frac{1}{2} + i\left( { - \frac{{\sqrt 3 }}{2}} \right)} \right) \cr
& = - 3 - 3\sqrt 3 i \cr} $$
