The argument of a complex number z=a+bi, denoted by arg(z), is the angle θ between the positive real axis and the line connecting origin to the point (a,b) in the complex plane. The measure of angle θ is the arctangent of the ratio of the y-coordinate to the x-coordinate of the point. θ = arctan (b/a) This measure is typically expressed using radians. For example, consider a complex number 2+2i. Its argument can be found by calculating arctan ( 22). arctan (2/2) =arctan (1) = π/2 The argument of 2+2i is π2.