In the link, I cant understand that why the Principal Unit Normal Vector is defined by N(t) = T'(t) / | T'(t) | ,can someone explain....
The Attempt at a Solution
Since tangent vector is normal to principal normal vector, why the N(t) shouldn't be -1 / ( T'(t) / | T'(t) | ) , since we know that if two vectors ( A and B) are prependicular to each other, then A multiply by B will get -1,
so, N(t) shouldn't be -1 / ( T'(t) / | T'(t) | ),
am i right? why we must differentiate it?