如下图所示,脖子区域的分解图为 \[ D_\delta^+\setminus D_{r_nR}^+(x_n) =D_\delta^+\setminus D_{\delta/2}^+(x_n’) \cup D_{\delta/2}^+(x_n’)\setminus D_{2d_n}^+(x_n’) \cup D_{2d_n}^+(x_n’)\setminus D_{d_n}^+(x_n) \cup D_{d_n}^+(x_n)\setminus D_{r_nR}^+(x_n). \]
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如下图所示,脖子区域的分解图为 \[ D_\delta^+\setminus D_{r_nR}^+(x_n) =D_\delta^+\setminus D_{\delta/2}^+(x_n’) \cup D_{\delta/2}^+(x_n’)\setminus D_{2d_n}^+(x_n’) \cup D_{2d_n}^+(x_n’)\setminus D_{d_n}^+(x_n) \cup D_{d_n}^+(x_n)\setminus D_{r_nR}^+(x_n). \]