明天8点之前急用!相似三角形的数学题~555555555555

由相似：
EF/AB=DF/BD
EF/CD=BF/BD
两式相加
EF(1/AB+1/CD)=(DF+BF)/BD=1
所以1/AB+1/CD=1/EF
2.1/ABD+1/BCD=1/EBD
同底.
分别作垂线,高的比和AB,CD,EF的比相同

创造是人的才能的最高表现形式,是推动人类社会前进的车轮.纵观历史,每一位取得卓越成就的人,无不是敢于创新的.敢于创新,是一种极可宝贵的精神,我们都应该学习.
小学的一篇课文《第三只小板凳》中写了这样一个故事：世界闻名的大科学家爱因斯坦在读小学时,一次劳作课后,他给老师交了一只做得很粗陋的小板凳.当老师看了极不满意时,他从课桌下又拿出第一次、第二次做的小板凳……爱因斯坦做出了第一只小板凳,为何不就此罢休而又做了两次,直到自己认为满意时才交给老师?这是因他具有创新精神.正因为有这种创新精神的支配,他才成了举世闻名的科学家.
大约2300年前,希腊有一位伟大的思想家亚里士多德,他认为物体落下的速度和重量成比例.约莫400年前,意大利的科学家伽利略并不因为亚里士多德说过了什么就轻易相信,他通过实验,推翻了亚里士多德的观点,建立了自由落体定律：一切物体如果不受空气的阻力,在同一地点自由落体运动中的加速度都相同.伽利略有如此的创新精神,便建立了物理学中的自由落体定律、惯性定律,并发现了抛体运动规律、摆振运动规律等.
有人说第一个用鲜花来比喻少女的人,受到人们一致的称赞,被誉为天才；第二个套用比喻的人,则被人们讥为庸才；等到第三个仍用此比喻的人,就被人们斥为蠢材了.这种说法未免夸张,但其中赞扬创新的意思却是无可非议的真理.
雨果说得好：“即使你成功地模仿了一个有天才的人,你也缺乏他的独创精神,这就是他的天才.我们来赞美大师吧,但不要模仿他们.还是让我们别出心裁吧,如果成功了,当然很好,如果失败,又有什么关系呢?”
我们应提倡创新,而且要敢于创新,而不去步人后尘,拾人牙慧.年轻的朋友们,趁我们正值青春年华,努力吧,愿我们有所创新,有所发明!
Innovation is the man to the highest expression of form,is to promote the wheel of human social advancement.Throughout history,each made outstanding achievements,all without exception is innovative.Dare to innovation,is a very precious spirit,we should learn.
Primary school text "the third one small wooden bench" wrote a story:the world-famous great scientist Albert Einstein reading elementary school,a work after class,he gave the teacher made a do very rough small wooden bench.When the teacher looked at very satisfied,he from the desk and take out the first,second do small wooden bench.Einstein made the first small wooden bench,why not take no for an answer and two times,until you think to the satisfaction with the teacher?This is because he has the innovation spirit.Just because of this spirit of the new control,he became world famous scientists.
About 2300 years ago,Greece has a great thinker Aristotle,he thought that the object of falling speed and weight in proportion.About 400 years ago,Italian scientist Galileo was not because Aristotle said what they believe,he through experiment and the overthrow of the Aristotle's point of view,and set up of free fall:all bodies if not affected by the resistance of the air,and in the same place in the movement of free fall acceleration are the same.Galileo has so spirit of innovation,and established the physics of free fall,inertia laws,and found the body movement rules,cast shimmy motion law,etc.
Some say the first girl with flowers to describe "the people,by the people of consistent praise,known as genius; The second set of metaphor,are people for mediocrity manner; Wait until the third still use this parable,regarded by people ChiWei fool.This statement is exaggerated,but among them praise the meaning of innovation is the truth of the above criticism.
Hugo said:"even if you successfully mimic a man of genius,you also lack his original spirit,this is his genius.We praise to master it,but don't imitate them.And let's try to be unique,if successful,of course,is very good,if failed,what does it matter?"
We should promote innovation,and dare to innovate,and not to step behind someone,SheRenYaHui.The young friends,while we when youth,work hard,we would like to make innovation,have invented!

Dear mom and dad,
How it's going?Today is January 13th,2011.After a few days,I can leave my school.I feel very happy,because I want to go sightseeing in Sanya during the winter vacation with my friends.Sanya is in Hainan Province in Southern China,the weather there is still warm in winter,so I can go to the beach and visit some scenic spots.Now I am writing the letter to you that I can't go home to spend the Spring Festival with you.I feel very sorry for that,but I sincerely hope you have a good time during those days.See you soon.
Best wishes!
Your son/daughter,
Your name

1 Let's meet in front of our school 8 o'clock tommorrow
2 My home is near to the school
3 I look forward to visiting the Great Wall again
4 Nobody knows what happened.
5 Great changes happened in my hometown during the past 10 years.
6 You had better not touch those things.

1.证明：因为BA//EF,所以EF/AB=FD/BD
因为DC//EF,所以EF/CD=BF/BD
所以EF/AB+EF/CD=FD/BD+BF/BD=1
提取EF,化简得1/AB+1/CD=1/EF

1.8km/分