Hi,

Guidance is appreciated.Thanks.

Prove that ∫∫∫_{v}∇f.∇gdV+∫∫∫_{v}f∇²gdV=∫∫_{s}f∇g.ndS

V is closed bounded region in space ,whose boundary is piecewise smooth orientable surface S.

n is an outwards pointing unit normal vector to S.

f and g are scalar functions with continuous second partial derivatives.