alias(v=vector):i:=v([1,0,0]):j:=v([0,1,0]):k:=v([0,0,1]): len := proc(u) sqrt(innerprod(evalm(u),evalm(u))); end: L := Int( len( diff( x*i + f(x)*j, x) ), x=a..b ); Dr := diff(x*i + f(x)*j, x); T := Dr / len( Dr ); K := len( diff(T,x) ) / len( Dr ); K := sqrt( simplify(K^2) ); f := x -> x^2; k := unapply(K,x); k0 := simplify(k(0)); k1 := simplify(k(1)); k1f := evalf(k1,2); Limit(k(x),x=infinity) = limit(k(x),x=infinity);