c. (2(2)^0.5,-2(2)^0.5)................................................................................................................................................

b. x component=4*cos(−2π/3)=-2, y component=4*sin(−2π/3)=-2*(3)^0.5

c. x component=-4*cos(3π/4)=2(2)^0.5, y component=-4*sin(3π/4)=-2(2)^0.5

if you don't understand my answer you can calculate it yourself, I already gave you the steps to calculate them. Remember to set the calculator into radian mode.