How to draw unit normal vector?

I have done all , except for the part plot unit normal vector.

Could you help we solving it, thanks a lot <3

[Torsten]

quiver3(x0,y0,z0,x0*(1+1/norm([x0,y0,z0])),y0*(1+1/norm([x0,y0,z0])),z0*(1+1/norm([x0,y0,z0])))

Answer 1

[Matt J]

Does the normal vector have to look like an arrow? If not, then with [nx,ny,nz] as the unit normal, you could do,

line([x0,x0+nx], ...
     [y0,y0+ny],
     [y0,y0+nz])

Answer 2

[Matt J]

Once you've plotted the sphere and plane, then with [nx,ny,nz] as the unit normal,

hold on
quiver3(x0,y0,z0, nx,ny,nz);
hold off