Let z, w be two complex numbers such that z¯ +iw¯ =0 and arg(zw)=π, then argz equal
3π4
π2
π4
5π4
z¯ +iw¯ =0 ⇒ z-iw=0
Now, arg(zw)=π ⇒ argz2i=π⇒ 2arg(z)-arg(i)=π⇒ 2arg(z)=π+π2=3π2⇒ arg(z)=3π4