2. ( 2 3.6 ) Let (s) be a Ck curve in the (x,y) plane, k2. Prove that if =0 then 0. (Hint: There are differentiable functions x(s) and y(s) such that (s)= (x(s),y(s),0). Show that B=(0,0,1).) Hint T=(x(s),y(s),0)T=(x(s),y(s),0)=N, and B=TN. 2. ( 2 3.6 ) Let (s) be a Ck curve in the (x,y) plane, k2. Prove that if =0 then 0. (Hint: There are differentiable functions x(s) and y(s) such that (s)= (x(s),y(s),0). Show that B=(0,0,1).) Hint T=(x(s),y(s),0)T=(x(s),y(s),0)=N, and B=TN