EE4206/EE5806 Image Processing -- tut#7 Laplacian operation is isotropic : answer

EE4206/EE5806 Image Processing tut#7 answer
Show that the Laplacian operation is isotropic (invariant to
rotation).

lecture 6
http://faraday.ee.emu.edu.tr/ee583/

唐宋八家文讀本--巻1-30 : 沈徳潛 評点, 頼山陽 増評
http://archive.wul.waseda.ac.jp/kosho/i13/i13_01056/