Find the fourth roots of unity by using the method stated.
a. Solve the polynomial equation x^4 = 1 algebraically.
b. Use the polar form z^4 = r(cos(theta) + sin(theta)), and find the modulus and argument of z.
c. Solve (a + bi)^4 = 1 by expanding (a + b)^4 and setting it equal to 1 + 0i.