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\mathrm{At}(0,0), \mathrm{m}_{\tan }=\lim\limits_{h \rightarrow 0} \frac{f(0+h)-f(0)}{(0+h)-(0)}=\lim\limits_{h \rightarrow 0} \frac{(0+h)^{2}-(0)^{2}}{h}=\lim\limits_{h \rightarrow 0} \frac{h^{2}}{h}=\lim\limits_{h \rightarrow 0} \mathrm{~h}=\mathbf{0}