$$r(t) = a\cos(t)i+b\sin(t)j+ctk$$ So this is the equation of a curve for which I've had trouble calculating it's unit vectors, especially $B$ and $N$.
I know that $T = v/|v|$ and that also $B = v × a / |v \times a|$, but when it comes to calculating $N= (dT/dt)/(|dT/dt|)$ it becomes impossible for me to calcite the dervative of $T$ with respect to $t$.