\[ f(x)\stackrel{\mathrm{def.}}{=}x^2+2x+3,\quad g(x)\overset{\mathrm{def.}}{=}3x^2+2x+1,\quad h(x)\underset{\mathrm{def.}}{=}\sin x. \] |
\[ \lim_{y=kx\atop (x,y)\to(0,0)}\frac{x y}{x^2+y^2} = \lim_{\genfrac{}{}{0pt}{1}{y=kx}{(x,y)\to(0,0)}}\frac{x y}{x^2+y^2} \] |
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桂田 祐史