For each of the given vectors, give a vector that, when added to it, yields a null

Question:

For each of the given vectors, give a vector that, when added to it, yields a null vector (a vector with a magnitude of zero). Express the vector in the form other than that in which it is given (component or magnitude– angle):
(a) A-bar = 4.5 cm, 40o above the +x-axis;
(b) B-bar = (2.0 cm) x-bar – (4.0 cm) y-bar;
(c) C-bar = 8.0 cm at an angle of 60o above the – x axis.