Mathematics, Vector Calculus, Learning Mathematics, Math.
likewise for the normal vector. The answer Herb gives in exercises 2.3.1 b and 2.3.1 d is illuminating. dR/dt (and thus dR/ds) gives us a tangent vector “in the direction” of the curve because ΔR is in the same plane as R for small values (and dR/dt is a scalar multiplication of ΔR). Similarly, if