Q.

Let O be the origin, the point A be z1=3+22i, the point B(z2) be such that 3|z2|=|z1| and arg(z2)=arg(z1)+π6. Then          [2025]

1 area of triangle ABO is 113  
2 ABO is an obtuse angled isosceles triangle  
3 ABO is a scalene triangle  
4 area of triangle ABO is 114  

Ans.

(2)

We have, z1=3+22i; 3|z2|=|z1| and arg(z2)=arg(z1)+π6

⇒ arg(z2)–arg(z1)=π6

∴  z2=|z2||z1|·z1ei(π/6)

            =13[(3+22i)(3+i)2]

⇒  z2=123[3–22+i(26+3)]

Now, z1–z2=3+22i–(3–22+i)(26+3)23

                      =6+46i–3+22–26i–i323

                       =3+22+i(26–3)23                      ∴  |z1-z2|=|z2|

⇒    △ABO is isosceles with angles π6,π6 and 2π3.

∴   Area of △ABO = 1211×113sinπ6=1143.