If z=20i-21+20i+21,than one of the possible value of |arg (z)| equals

20i+21 =(5+2i)2  and 20i+21 =(2-5i)2 ∴        z=±(5+2i)±(2+5i) ⇒        z=7(1+i), 3(1-i), 3(-1+i), (-1-i) ⇒      arg(z)= π/4, -π/4, 3π/4, -3π/4      Thus, one of the possible value of |arg(z)| is π/4.