"Green's function" # Note: In Eigenmath, div(grad(1/r)) == 0 G = -exp(i k r) / (4 pi r) r = sqrt(x^2 + y^2 + z^2) "Verify equation (6)" check(-4 pi div(grad(G)) == dot(grad(1/r),grad(exp(i k r))) + div(grad(exp(i k r))) / r + dot(grad(1/r),grad(exp(i k r))) + exp(i k r) div(grad(1/r)) ) "ok" "Verify equation (7)" check(dot(grad(1/r),grad(exp(i k r))) == -i k exp(i k r) / r^2) "ok" "Verify equation (8)" check(div(grad(exp(i k r))) / r == 2 i k exp(i k r) / r^2 - k^2 exp(i k r) / r) "ok" "Verify equation (9)" check(div(grad(G)) == -k^2 G) "ok" Run