Let $ P(x_1, y_1) $ and $ Q(x_2, y_2) $ be two distinct points on the ellipse $$ \frac{x^2}{9} + \frac{y^2}{4} = 1 $$ such that $ y_1 > 0 $, and $ y_2 > 0 $. Let $ C $ denote the circle $ x^2 + y^2 = 9 $, and $ M $ be the point $ (3, 0) $. Suppose the line $ x = x_1 $ intersects $ C $ at $ R $, and the line $ x = x_2 $ intersects $ C $ at $ S $, such that the $ y $-coordinates of $ R $ and $ S $ are positive. Let $ \angle ROM = \frac{\pi}{6} $ and $ \angle SOM = \frac{\pi}{3} $, where $ O $ denotes the origin $ (0, 0) $. Let $ |XY| $ denote the length of the line segment $ XY $. Then which of the following statements is (are) TRUE?
It is a set of 3 mutually perpendicular axes and a convenient way to represent a set of numbers (2 or 3) or a point in space.

Hence, we have a way to represent an imaginary number graphically. All we need to do is to find the real part and an imaginary part of it. Then, represent them on the two mutually perpendicular number lines. The point of intersection, as shown in the above diagram, is the origin of our Plane.
The formation of the Plane so formed is known as the Argand Plane and it is a convenient way to represent an imaginary number graphically.