Originally Posted by

**clombard1973** Hi there,

So you are close with your result for a unit vector tangent. It is actually:

T(t) = (4t/(4|t|))i = (t/|t|)i

The vector you got of simply i is only true when the variable t is positive, when it is negative your vector would point 180 degrees out of phase.

A normal unit vector will point perpendicular to the curve at all points. Now since i points along the x axis you know that perpendicular to this is the y axis which uses the unit vector j.

The easiest solution is to simply make the normal unit vector the unit tangent vector at 90 degrees, so....

N(t) = (t/|t|)j

I think this will work....good luck,

Craig