[Denman]

Originally Posted by Alan Anderson

It's another example of roots gone bad:

There are four 4th roots of 1:
1
-1
i
-i
Raise any of these to the 4th power and you get 1.

The main thing to remember from this is that taking roots is not something you can safely do to both sides of an equation unless you can figure out which root is required in order to satisfy the result.

Aka the fourth roots of unity. You can take roots from any imaginary number. If you think about it geometrically using argand diagrams, the differences between the angle of the roots is the argument of the complex number.
I'll post a better thing tomorrow or when i'm thinking lol