Polar form of a complex number is r( cos(theta) + i sin(theta) )
r is equal to the total distance created by the rectangular coordinates of the complex number
r = Root(4^2 + (-4)^2) = Root(32) = 4 Root(2)
To find theta, if a > 0, use arctan(b/a), where:
a = the first number
b = the second number
arctan (-4/4) = -45 degrees (-0.7854 radians)
Your answer is 4 Root(2) (cos(-45) + i sin(-45))