Question

How do you plot `5i`?

Answer 1

I tried this:

Explanation:

We can use the Complex Plane (aka, Argand-Gauss Plane) where on the horizontal axis you plot the real parts of a complex number while on the vertical one you plot the coefficient of the imaginary part.
So in your case you have a complex number in the form:
`z=0+5i`
the real part is zero while the imaginary is `5`.
You get:

The dot represents your complex number on the Complex Plane.

Answer 2

It's just a vertical vector along the yy axis with 5 measures long.

Explanation:

You have the x dimension for the real part and the y dimension for the imaginary part. If the real part is zero, your value is along the y axis graph{100000x [-5, 5., 0, 5]} .