i := vector([1,0,0]): j:=vector([0,1,0]): k:= vector([0,0,1]): f := t -> cos(t)*i + sin(t)*j + t*k; df := diff(f(t),t); Df := D(f); Tx := Df(x)/sqrt(innerprod(Df(x),Df(x))); Tx := simplify(Tx,trig); T := unapply(Tx,x); L1 := s -> f(t1) + s*Df(t1); L2 := t -> f(t2) + t*Df(t2); alias(dot=innerprod, cross=crossprod); vol := dot( f(t1)-f(t2), cross(Df(t1),Df(t2)) ); vol := simplify(vol,trig); vol1 := simplify(subs(t1=0,vol)); T2 := solve(vol1,t2);