Question

How do you find the absolute value of `-8i`?

Answer 1

`8`

Explanation:

Given a complex number like `z=x+iy` then `abs z` is defined as

`abs z = sqrt(z cdot \bar z` where `bar z = x-iy` is the `z` conjugate.

Then `absz=sqrt(x^2+y^2)`. In our case

`abs(-i8) = sqrt((-i8)(i8))` = 8

`abs z ge 0` by definition.