Take 15 minutes to prepare this exercise.
Then, if you lack ideas to begin, look at the given clue and start searching for the solution.
A detailed solution is then proposed to you.
If you have more questions, feel to ask then on the forum.
Write and as a polynomial in and
Use the formula of Moivre: develop the left term with the binomial formula then identify the real and imaginary parts.
We use Moivre's formula:
We develop the left term with the binomial formula:
Identifying real and imaginary parts, we get:
