> restart;

> with(plots):

> dp := proc(X,Y)

>     X[1]*Y[1]+X[2]*Y[2];

> end:

> nrm := proc(X)

>     sqrt(dp(X,X));

> end:

> r:=[3*cos(u),3*sin(u)];

> lambda:=1;

>  f:=proc(X)

> local Xu,s,T,N,kappa,v,n,pr,v1,z;

> Xu := [diff(X[1],u),diff(X[2],u)];

> s := nrm(Xu);

> T:=[diff(X[1],u)/s,diff(X[2],u)/s];

> N:=[-T[2],T[1]];

> kappa:=simplify(dp(diff(T,u),N))/s;

> v:=int(kappa,u=0..u);

> z:=v;

> if z=0 then -1 else  v1:=z fi;

> n:=[cos(v1)*N[1]+sin(v1)*T[1],cos(v1)*N[2]+sin(v1)*T[2]];

> pr:=([r[1]+lambda*n[1],r[2]+lambda*n[2]]);

> end:

> plot([f(r)[1],f(r)[2],-18..18]);

can you please help me , I'm not sure what is going wrong.