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Exprimez en coordonnées polaires : \(\displaystyle y^2 {\partial^n f\over \partial x^2} - 2xy {\partial^n f\over \partial x \partial y} + x^2 {\partial^n f\over \partial y^2} - x {\partial f\over \partial x} - y {\partial f\over \partial x}.\)
Exprimez en coordonnées polaires : \(\displaystyle y^2 {\partial^n f\over \partial x^2} - 2xy {\partial^n f\over \partial x \partial y} + x^2 {\partial^n f\over \partial y^2} - x {\partial f\over \partial x} - y {\partial f\over \partial x}.\)