r = (x^2 + y^2 + z^2)^(1/2)
i): Show that (Δ ∙ F) = 0 if F has the form kR/r^3 where r not equal to 0
(ii): Show that if F has the form kR/r^3
∫∫ F ∙ ndS = 4pi
where the boundary is the sphere of radius 1 center at (0,0,0)
更新1:
Δ = nabla