3. (a) Using the Frenet-Serret equations, prove that dr/ds d ²r/ds² d³rds ³ = / ² .

(b) Given that the Darboux rotation vector is given by w = T + B , use the Frenet-Serret frame (T , N , B ) to show that

i. dT/ds = w T

ii. dN/ds = w N.