The HTML file contains the "program"

input x(t)=sin(5t);
input y(t)=cos(3t);
input z(t)=2t-1;
hide $1(t)=diff(x(t),t);
hide $2(t)=diff(y(t),t);
hide $3(t)=diff(z(t),t);
hide $4(t)=sqrt($1(t)^2+$2(t)^2+$3(t)^2);
hide $5(t)=x(t)+$1(t)/$4(t);
hide $6(t)=y(t)+$2(t)/$4(t);
hide $7(t)=z(t)+$3(t)/$4(t);
scroller t0 0 1;
2D;
  point x(t0) y(t0) yellow;
  thick line x(t0) y(t0) $5(t0) $6(t0) green;
  thin Curve x(t) y(t) t 0 1 red;
3D;
  box;
  point x(t0) y(t0) -1 green;
  Curve x(t) y(t) -1 t 0 1 red;
  point x(t0) y(t0) z(t0) yellow;
  thick line x(t0) y(t0) z(t0) $5(t0) $6(t0) $7(t0) green;
  thin;
    Curve x(t) y(t) z(t) t 0 1 white;
    Curve x(t) -1 z(t) t 0 1 blue;
  thick;
    line x(t0) -1 z(t0) $5(t0) -1 $7(t0) green;
    line x(t0) y(t0) -1 $5(t0) $6(t0) -1 green;
  point x(t0) -1 z(t0) green;
2D;
  point x(t0) z(t0) yellow;
  Curve x(t) z(t) t 0 1 blue;
  thick line x(t0) z(t0) $5(t0) $7(t0) green;
value We_can_see_that_t0^2# t0^2 red;