Q.

Let w1 be the point obtained by the rotation of z1=5+4i about the origin through a right angle in the anticlockwise direction, and w2 be the point obtained by the rotation of z2=3+5i about the origin through a right angle in the clockwise direction. Then the principal argument of w1-w2 is equal to          [2023]
 

1 -π+tan-1335  
2 π-tan-1335  
3 -π+tan-189  
4 π-tan-189  

Ans.

(4)

w1=z1i=(5+4i)i=-4+5i 

w2=z2(-i)=(3+5i)(-i)=5-3i 

w1-w2=-9+8i 

Principal argument=π-tan-1(89)