z1z2=(r1r2)(cos(θ1−θ2)+isin(θ1−θ2))
z1=−7+i3,z2=−9−i3
r1=√72+32=√58
θ1=tan−1(3−7)=−tan⋅−1(−37)=−23.2∘=156.8∘, II Quadrant
r2=√92+32=√90
θ2=tan−3−9=tan−1(13)=18.43∘198.43∘, III Quadrant
z1z2=√5890(cos(156.8−198.43)+isin(156.8−198.43))
⇒0.8028(0.7475−i0.6643)