1. The problem statement, all variables and given/known data Let [itex] c(t) = ( cos(At), sin(At), 1) [/itex] be a curve. (A is a constant) Show that the normal to [itex] c(t) [/itex] is always directed toward the z-axis. 3. The attempt at a solution I am not sure how to show this. (For example, is the question "asking" us to show the cross product of something is 0 ?) If you tell me how to start the problem, I should have no problem. I have found the normal, which is [itex] N(t) = ( -cos(At), -sin(At), 0) [/itex]. Thanks.