=== Imaginary Number ===

The imaginary number `sqrt(-1)` is written in Poi as `imag` or `𝐢`.
In the form `(a + b * imag)` one gets the theory of complex numbers.

In mathematics, complex numbers usually refers the form `(a + b * imag)`,
but in general there are other bases and algebras, such as dual numbers.

Complex numbers are very useful because they naturally represent circle-like
operations and provides solutions to equations when there are no real solutions.
One can use vectors and matrices instead of complex numbers, which is common,
so it is a good idea to learn how to translate math between the two forms.

When you multiply two complex numbers in vector form, you use the formula
`mulc([a0, b0], [a1, b1])`, but in the form `(a + b * imag)` you can use
normal multiplication `((a0 + b0 * imag) * (a1 + b1 * imag))`.

Poi understands e.g. `(2 + 3imag)` or `(2 + 3𝐢)` as `(2 + 3 * imag)`.