Q9. (10 pts) We know that Euler's formula is = cos 0 + i sin 0 e130 = cos 30 + i sin 30 Now, use this relation e130 e130 = (elv) to prove: 1) cos 30 = 4 cos3 0 - 3 cos 0; 2) sin 30 = 3 sin 0 - 4 sin3 0