⊙O的两条弦AB、CD相交于点P,已知AP=2cm,BP=6cm,CP:PD=1:3,则CD=______.
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⊙O的两条弦AB、CD相交于点P,已知AP=2cm,BP=6cm,CP:PD=1:3,则CD=______. |
答案
∵⊙O的两条弦AB、CD相交于点P, ∴PA×PB=PC×PD, 又∵AP=2cm,BP=6cm,CP:PD=1:3, ∴设PC=x,PD=3x,可得2×6=3x2,解之得x=2(舍负) 因此CD=4x=8. 故答案为:8 |
举一反三
如图,圆O的直径AB=6,CD是圆O的弦,BA,DC的延长线交于点P,若PA=4,PC=5,求CD及∠CBD.
![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234307-20906.png) |
(几何证明选讲选做题)如图,半径为2的⊙O中,∠AOB=90°,D为OB的中点,AD的延长线交⊙O于点E,则线段DE的长为______.
![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234303-70188.png) |
已知:如图,一个圆的两条弦AB和CE相交于点D,BE=2,BC=2BD=2,∠1=∠2则EC=______,∠CBE=______.
![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234259-34457.png) |
如图,四边形ABCD内接于⊙O,![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234254-73958.png) | AB | =![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234254-73958.png) | AD | ,过A点的切线交CB的延长线于E点.求证:AB2=BE•CD.
![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234255-16969.png) |
选修4-1:几何证明选讲 如图,已知四边形ABCD内接于ΘO,且AB是的ΘO直径,过点D的ΘO的切线与BA的延长线交于点M. (1)若MD=6,MB=12,求AB的长; (2)若AM=AD,求∠DCB的大小.
![](http://img.shitiku.com.cn/uploads/allimg/20191107/20191107234251-47230.png) |
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