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#ace016d4-f3d0-451c-8b46-8c64b1fc40b3基础fill_compute椭圆标准方程与性质直线与圆+圆锥曲线

18. 已知F1F_{1}F2F_{2}分别为椭圆C:y2a2+x2b2=1(a>b>0)C:\frac{{y}^{2}}{{a}^{2}}+\frac{{x}^{2}}{{b}^{2}}=1(a>b>0)的两个焦点,右顶点为AADDAF2AF_{2}的中点,且F1DAF2F_{1}D\bot AF_{2},直线F1DF_{1}DCC交于MMNN两点,且ΔAMN\Delta AMN的周长为28,则椭圆CC的短轴长为 ___737\sqrt{3}___.