Let r = (x, y, z) and e r =r/ r. Show that if a function (x, y, z) = F(r) depends only on the

Let r = (x, y, z) and e_r =r/ ΙΙrΙΙ. Show that if a function ƒ(x, y, z) = F(r) depends only on the distance from the origin r = ΙΙrΙΙ= √x² + y² + z², then

Vf = F'(r)er