Hello, scrappy!
Exactly where is your difficulty?
. . Multiply it out . . .
Find: .
. . . . . .
. . . . . .
. . . . . .
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
If you are familiar with DeMoivre's Theorem, it's faster.
Since
. . we have: .
Then: .