z1 := x^2*y + 3*x*y^3; x := exp(t); y := sin(t); t0 := 0; answer1 := diff(z1,t); answer1 := simplify(subs(t=0,answer1)); x := 'x': y := 'y': z := x^2*y + 3*x*y^3; zx := diff(z,x); zy := diff(z,y); xt := diff(exp(t),t); yt := diff(sin(t),t); x := exp(t): y := sin(t): zt := 'zx'*'xt' + 'zy'*'yt'; answer := simplify( subs(t=0,zt) ); with(plots): C := spacecurve([x,y,z],t= -1..1,color=yellow): S := plot3d(x1^2*y1 + 3*x1*y1^3,x1=-1..1,y1=-1..1.5): display3d({S,C},axes=frame,orientation=[83,56]);