将圆\(x^{2}+y^{2}=4\)上每一点的纵坐标保持不变,横坐标变为原来的\(2\)倍,得曲线\(C\).
\((1)\)求曲线\(C\)的标准方程;
\((2)\)设直线\(l\):\(x-2y+4=0\)与\(C\)的交点为\(P_{1}\),\(P_{2}\),以坐标原点为极点,\(x\)轴正半轴为极轴建立极坐标系,求以线段\(P_{1}P_{2}\)为直径的圆的极坐标方程.
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