Find Torque About Any Line: How to Calculate n Vector

[Vertol]

I know how to find a torque at anyone point, and about the x,y, and z axis.

General equation is t = n dot (r X F)

where t is the torque, n is unit vector

I know that to find torque about any axis, suppose the y-axis then n=(0,1,0) However, I don't know how to find n of any line.
I am working on a practice problem for a test where the line is x/2 = y/1 = z/-2

Any help would be appreciated.

 

[willem2]

find 2 points on the line, use the position vector of point2 - point1.

If this vector has length 1 you're done. If not, multiply the vector by
some constant to make the length equal to 1.