优优班--学霸训练营 > 知识点挑题
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            • 1.
              如图,在\(\triangle ABC\)和\(\triangle ACD\)中,\(∠ACB=∠ADC=90^{\circ}\),\(∠BAC=∠CAD\),\(⊙O\)是以\(AB\)为直径的圆,\(DC\)的延长线与\(AB\)的延长线交于点\(E\).
              \((\)Ⅰ\()\)求证:\(DC\)是\(⊙O\)的切线;
              \((\)Ⅱ\()\)若\(EB=6\),\(EC=6 \sqrt {2}\),求\(BC\)的长.
            • 2.
              已知如图,四边形\(ABCD\)为圆内接四边形,\(AB\)是直径,\(MN\)切\(⊙O\)于\(C\)点,\(∠BCM=38^{\circ}\),那么\(∠ABC\)的度数是\((\)  \()\)
              A.\(38^{\circ}\)
              B.\(52^{\circ}\)
              C.\(68^{\circ}\)
              D.\(42^{\circ}\)
            • 3.
              如图,\(AB\)是半圆的直径,\(C\)是\(AB\)延长线上一点,\(CD\)切半圆于点\(D\),\(CD=2\),\(DE⊥AB\),垂足为\(E\),且\(E\)是\(OB\)的中点,求\(BC\)的长.
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