(−6+i)+(9+3i)
z=x+iy
z=r(cosθ+isinθ)
r=|z|=∣∣∣√x2+y2∣∣∣
r1=√−62+12=√37
θ1=arctan(yx)=tan−1(1−6)=170.5377∘, II Quadrant
r2=√92+32=√90
θ2=arctan(yx)=tan−1(39)=18.4349∘, I Quadrant
(−6+i)+(9+3i)=√37(cos170.5377+sin170.5377)+√90(cos18.4349+sin18.4349)
⇒√37cos170.5377+√90cos18.4349+i(√37sin170.5377+√90sin18.4349)
⇒−6+9+1i+3i
(−6+i)+(9+3i)=3+4i, I Quadrant