This is a sample problem in the text that I am having problems comprehending. 1. The problem statement, all variables and given/known data A car is traveling northwest at 9.00 m/s. Eight seconds later it has rounded a corner and is headed north at 15.00 m/s. What are its magnitude and direction of its average acceleration during those eight seconds? 2. Relevant equations ∆v = V_f - V_i (vectors) 3. The attempt at a solution The problem shows its strategy, but wants the student to do the calculations for each step. Step 1: Write out V_i. Vector V_i=9m/s = -6.36m/s xhat + 6.36m/s yhat. I'm OK here. I know how to get velocity vectors and I worked this out correctly. Step 2: Write out V_f. Vector V_f = 15m/s. I guess this is just a given. OK .... Step 3: Calculate ∆V. ∆V= 6.36m/s xhat + 8.64m/s yhat. I don't know why the xhat is positive all of a sudden, but I understand that a turn due north adds zero to the xhat. I have no idea where the number for yhat is coming from. There's a step 4 and 5, but if I can understand this part, I think I can work those out. Thanks in advance. On a side note, how the heck can I type the symbols for hat, vectors, subscripts, etc.?