Let z be a complex number such that the principal value of argument, argz>0. Then argz–arg(–z) is
Principal Value
Quad I=θ
Quad II=π−θ
Quad III=θ−π
Quad IV=−θ
If argz=θ>0
⇒ Complex number (z) lies in the I or II quadrant.
⇒−z lies in the III or IV quadrant.
Case:1-
z lies in I quadrant ⇒argz=θ
⇒−z lies in III quadrant ⇒arg(−z)=θ−π
∴argz−arg(−z)=π
Case:2-
z lies in II quadrant ⇒argz=π−θ
⇒−z lies in IV quadrant ⇒arg(−z)=−θ
∴argz−arg(−z)=π