共50条信息
如图,在\(\triangle ABC\)中,\(D\),\(E\)分别是\(AB\),\(AC\)上的点,\(DE/\!/BC\),若\(AD=1\),\(BD=3\),则\(\dfrac{DE}{BC}\)的值为________.
如图,已知三角形\(ABC\)的边\(AB\)是\(⊙O\)的切线,切点为\(B.AC\)经过圆心\(0\)并与圆相交于点\(D\)、\(C\),过\(C\)作直线\(CE\)丄\(AB\),交\(AB\)的延长线于点\(E\).
\((1)\)求证:\(CB\)平分\(∠ACE\);
\((2)\)若\(BE=3\),\(CE=4\),求\(⊙O\)的半径.
如图,\(\triangle A′B′C′\)是\(\triangle ABC\)在以点\(O\)为位似中心经过位似变换得到的,若\(\triangle ABC\)的面积与\(\triangle A′B′C′\)的面积比是\(16\):\(9\),则\(OA\):\(OA′\)为( )
如图,在\(\triangle ABC\)中,\(D\),\(E\)分别为\(AB\),\(AC\)边上的点,\(DE/\!/BC\),\(BE\)与\(CD\)相交于点\(F\),则下列结论一定正确的是( )
在\(\triangle ABC\)中,\(D\)、\(E\)分别是\(AB\)、\(AC\)上的点,\(DE/\!/BC\),\(\dfrac{AD}{DB}=\dfrac{1}{2}\),则下列结论中正确的是\((\) \()\)
如图,\(AB\)为\(⊙O\)直径,\(C\)、\(D\)为\(⊙O\)上不同于\(A\)、\(B\)的两点,\(∠ABD=2∠BAC\),连接\(CD.\)过点\(C\)作\(CE⊥DB\),垂足为\(E\),直线\(AB\)与\(CE\)相交于\(F\)点.
\((1)\)求证:\(CF\)为\(⊙O\)的切线;
\((2)\)当\(BF=5\),\(\sin F=\dfrac{3}{5}\)时,求\(⊙O\)的半径.
如图,四边形\(ABCD\)中,\(AB/\!/CD \),点\(F\)在\(BC\)上,连\(DF\)与\(AB\)的延长线交于点\(G\),\(E\)是\(AD\)的中点
\((1)\)求证:\(∆CDF∽∆BGF \);
\((2)\)当点\(F\)是\(BC\)的中点时,若\(AB=6cm \),\(EF=4cm \),求\(CD\)的长.
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