so i understand part a, but I dont understand how to do part b. please help! You are given a vector in the xy plane that has a magnitude of 90.0 units and a y component of -40.0 units. (a) What are the two possibilities for its x component? I got 80.6 and -80.6. (b) Assuming the x component is known to be positive, specify the vector which, if you add it to the original one would give a resultant vector that is 90.0 units long and points entirely in the -x direction. What is the magnitude and direction?