如图,AB是⊙O的直径,BD是⊙O的弦,延长BD到点C,使DC=BD,连接AC,过点D作DE⊥AC,垂足为E.
(1)求证:AB=AC;
(2)若⊙O的半径为4,∠BAC=60°,求DE的长.
考点分析:
相关试题推荐
(1)解方程:2x
2-5x+2=0;
(2)已知|a-2|+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546018_ST/0.png)
=0,计算
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546018_ST/1.png)
的值.
查看答案
观察下列计算:
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/0.png)
•(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/1.png)
+1)=(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/2.png)
-1)(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/3.png)
+1)=1,
(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/4.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/5.png)
)(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/6.png)
+1)=[(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/7.png)
-1)+(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/8.png)
-
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/9.png)
)](
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/10.png)
+1)=2,
(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/11.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/12.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/13.png)
)(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/14.png)
+1)=[(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/15.png)
-1)+(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/16.png)
-
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/17.png)
)+(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/18.png)
-
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/19.png)
)](
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/20.png)
+1)=3,
…
从以上计算过程中找出规律,并利用这一规律进行计算:
(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/21.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/22.png)
+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/23.png)
+…+
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/24.png)
)(
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131022164127613954655/SYS201310221641276139546017_ST/25.png)
+1)=
.
查看答案
正方形OABC在坐标系中的位置如图所示,将正方形OABC绕O点顺时针旋转90°后,B点的坐标为
.
查看答案
小华的妈妈为爸爸买了一件衣服和一条裤子,共用306元.其中衣服按标价打七折,裤子按标价打八折,衣服的标价为300元,则裤子的标价为
元.
查看答案
如图,在四边形ABCD中,AB=BC=CD=DA,对角线AC与BD相交于点O,若不增加任何字母与辅助线,要使四边形ABCD是正方形,则还需增加一个条件是
.
查看答案