等腰三角形復習講義

1、等腰三角形復習講義【回顧與思考】 等腰三角形【例題經(jīng)典】根據(jù)等腰三角形的性質(zhì)尋求規(guī)律例1在abc中，ab=ac，1=abc，2=acb，bd與ce相交于點o，如圖，boc的大小與a的大小有什么關(guān)系？ 若1=abc，2=acb，則boc與a大小關(guān)系如何？若1=abc，2=acb，則boc與a大小關(guān)系如何？【分析】在上述條件由特殊到一般的變化過程中，根據(jù)等腰三角形的性質(zhì)，1=2，abd=ace，即可得到1=abc，2=acb時，boc=90+a；1=abc，2=acb時，boc=120+a；1=abc，2=acb時，boc=180+a 【點評】在例1圖中，若ae=ab，ad=ac類似上題方法同樣可

2、證得bd=ce上述規(guī)律仍然存在會用等腰三角形的判定和性質(zhì)計算與證明例2如圖，等腰三角形abc中，ab=ac，一腰上的中線bd將這個等腰三角形周長分成15和6兩部分，求這個三角形的腰長及底邊長 【分析】要分ab+ad=15，cd+bc=6和ab+ad=6，cd+bc=15兩種情況討論利用等腰三角形的性質(zhì)證線段相等例3（2006年常德市）如圖，p是等邊三角形abc內(nèi)的一點，連結(jié)pa、pb、pc，以bp為邊作pbq=60，且bq=bp，連結(jié)cq （1）觀察并猜想ap與cq之間的大小關(guān)系，并證明你的結(jié)論（2）若pa：pb：pc=3：4：5，連結(jié)pq，試判斷pqc的形狀，并說明理由 【分析】（1）把ab

3、p繞點b順時針旋轉(zhuǎn)60即可得到cbq利用等邊三角形的性質(zhì)證abpcbq，得到ap=cq（2）連接pq，則pbq是等邊三角形pq=pb，ap=cq故cq：pq：pc=pa：pb：pc=3：4：5，pqc是直角三角形 【點評】利用等邊三角形性質(zhì)、判定、三角形全等、直角三角形的判定等知識點完成此題的證明winger tuivasa-sheck, who scored two tries in the kiwis 20-18 semi-final win over england, has been passed fit after a lower-leg injury, while slater h

4、as been named at full-back but is still recovering from a knee injury aggravated against usa.both sides boast 100% records heading into the encounter but australia have not conceded a try since josh charnleys effort in their first pool match against england on the opening day.aussie winger jarryd ha

5、yne is the competitions top try scorer with nine, closely followed by tuivasa-sheck with eight.but it is recently named rugby league international federation player of the year sonny bill williams who has attracted the most interest in the tournament so far.the kiwi - with a tournament high 17 offlo

6、ads - has the chance of becoming the first player to win the world cup in both rugby league and rugby union after triumphing with the all blacks in 2011.id give every award back in a heartbeat just to get across the line this weekend, said williams.the (lack of) air up there watch mcayman islands-ba

7、sed webb, the head of fifas anti-racism taskforce, is in london for the football associations 150th anniversary celebrations and will attend citys premier league match at chelsea on sunday.i am going to be at the match tomorrow and i have asked to meet yaya toure, he told bbc sport.for me its about

8、how he felt and i would like to speak to him first to find out what his experience was.待添加的隱藏文字內(nèi)容2uefa hasopened disciplinary proceedings against cskafor the racist behaviour of their fans duringcitys 2-1 win.michel platini, president of european footballs governing body, has also ordered an immedia

9、te investigation into the referees actions.cska said they were surprised and disappointed by toures complaint. in a statement the russian side added: we found no racist insults from fans of cska. baumgartner the disappointing news: mission aborted.the supersonic descent could happen as early as sund

10、a.the weather plays an important role in this mission. starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. the balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere)

11、 where our day-to-day weather lives. it will climb higher than the tip of mount everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. as he crosses the boundary layer (called the tropopause)

12、,e can expect a lot of turbulence.the balloon will slowly drift to the edge of space at 120,000 feet ( then, i would assume, he will slowly step out onto something resembling an olympic diving platform.they blew it in 2008 when they got caught cold in the final and they will not make the same mistak

13、e against the kiwis in manchester.five years ago they cruised through to the final and so far history has repeated itself here - the last try they conceded was scored by englands josh charnley in the opening game of the tournament.that could be classed as a weakness, a team under-cooked - but i have

14、 been impressed by the kangaroos focus in their games since then.they have been concentrating on the sort of stuff that wins you tough, even contests - strong defence, especially on their own goal-line, completing sets and a good kick-chase. theyve been great at all the unglamorous stuff that often

15、goes unnoticed in the stands but not by your team-mates.it is as though their entire tournament has been preparation for the final.in johnathan thurston, cooper cronk, cameron smith and either billy slater or greg inglis at full-back they have a spine that is unmatched in rugby league. they have played in so many high-pressure games - a priceless asset going into saturday.the kiwis are a lot less