In most problems involving projections I'm given a vector and the equation of a line either in parametric form or in symmetric form (ie. parametric: <0t+3, -t-4. 3t+2> or symmetric form: x=3, (y+4)/-1, (z-2)/3). However, when asked to use these in a problem I get confused often. So my question is what does <0, -1, 3> and <3, -4, 2> each stand for? When is it appropriate to use one vector over the other?