1.) P(-1,2,3) and Q(4,0,1) are two points in space. Find the angle that PQ makes with the X-axis.

I got PQ to be (5,-2,-4). I know to use the formula for the angle between two vectors but I'm having trouble with the x-axis part. I know it is k(1,0,0), where k is a parameter. Since (1,0,0) is a direction on the x-axis, to have a line, k would be a parameter.

But with this unknown parameter, how am I to solve for the angle?

2.) Given P(2,-5,6) and Q(-1,7,9), find the distance from P to the x-axis.

Again the parameter problem, I can solve it without the parameter, so how should I go about this question?

3.) For A(2,-1,3) and B(0,1,-1), find the coordinates of C on AB which is 2 units from A.

How do I do this? I know it is something to do with ratio but I'm not sure..

Thank you so much!