Solution
When a complex number is written in its polar form, z=r(cos theta + i sin theta) , the angle theta is called the "argument" of z.
two same ways:
1.Geometrically, in the complex plane, as the angle from the positive real axis to the vector representing z. The numeric value is given by the angle in radians and is positive if measured counterclockwise.
2. Algebraically, as any real quantity such that
So, when the complex number is written in its polar form, the angle is called the argument of z.
Answer
"argument" of z.