Q9. (10 pts) We know that Euler's formula is el = cose + i sin 0 el30 = cos 30 + i sin 30 Now, use this relation e 30 = (el)3 to prove: 1) cos 30 = 4 cos3 0 - 3 cos 0; 2) sin 30 = 3 sin 0 - 4 sin$ 0