Se $$u=f(x,y)$$, $$x=r\cdot cos(\theta)$$ e $$y=r\cdot sen(\theta)$$, mostre que
\[(\frac{\partial u}{\partial x})^{2}+(\frac{\partial u}{\partial y})^{2}=(\frac{\partial u}{\partial r})^{2}+\frac{1}{r^{2}}(\frac{\partial u}{\partial \theta})^{2}.\]
Solução:
Coordenadas Polares e Regra da Cadeia
