Question

In polar representation of a complex number (r, π/2) lies on ____________

(a) x-axis

(b) y-axis

(c) z-axis

(d) any axis

I got this question by my college professor while I was bunking the class.

My question is from Argand Plane and Polar Representation topic in section Complex Numbers and Quadratic Equations of Mathematics – Class 11

Answer 1

Correct choice is (b) y-axis

To explain I would say: To convert polar representation (r, θ) into argand plane (x, y), substitute x=r cos θ and y=r sin θ.

x=r cos π/2 = 0 and y=r sin π/2 = r.

Argand plane representation is (0, r). Since real part is zero, so it lies on imaginary axis i.e. y-axis.