Let w be a negative real number, z a 6th root of w.
a) Show that z(k) = p^1/6 [cos ( pi + 2 * k* pi / 6) + i sin ( pi + 12 * k * pi / 6)], k = v, 1,2,3,4,5 is a formula for the 6th roots of w.
b) Hence determine 6th roots of - 729.
c) Given z = cosA + i sin A and u + iv = (1+z) (1+ z^2). Prove that v = u tan(3A/2), u^2 + v^2 = 16 cos ^2(A/2) cos^2A