共50条信息
在长方体\(ABCD—A_{1}B_{1}C_{1}D_{1}\)中,对角线\(B_{1}D\)与平面\(A_{1}BC_{1}\)相交于点\(E\),则点\(E\)为\(\triangle A_{1}BC_{1}\)的( )
如下图,\(PA\)是圆\(O\)的切线,切点为\(A,PO\)交圆\(O\)于两点,\(PA=\sqrt{3},PB=1\),则\(AC=\) .
如图,\(AE\)是圆\(O\)的切线,\(A\)是切点,\(AD⊥OE\)于\(D\),割线\(EC\)交圆\(O\)于\(B\)、\(C\)两点.
\((1)\)证明:\(O\)、\(D\)、\(B\)、\(C\)四点共圆;
\((2)\)设\(∠DBC=50^{\circ}\),\(∠ODC=30^{\circ}\),求\(∠OEC\)的大小.
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