三角函數(shù)講義2

1、第2講 同角三角函數(shù)的基本關(guān)系與誘導(dǎo)公式1、 考綱點(diǎn)擊（1）平方關(guān)系：（2）商數(shù)關(guān)系：（3）能利用單位圓中的三角函數(shù)線推導(dǎo)出的正弦、余弦、正切的誘導(dǎo)公式。2、熱點(diǎn)提示（1）利用誘導(dǎo)公式求值或化簡(jiǎn)三角函數(shù)是考查重點(diǎn)。（2）同角三角函數(shù)關(guān)系式用來化簡(jiǎn)，求值是高考熱點(diǎn)。（3）主要以選擇題、填空題的形式考查。知識(shí)整合：1：熟記特殊角的三角函數(shù)值：角030456090120135150180弧度數(shù)正弦余弦正切待添加的隱藏文字內(nèi)容32：誘導(dǎo)公式：（填表）正弦余弦可概括為：奇變偶不變，符號(hào)看象限如：sin390= cos（45）= tan（= 3、同角三角函數(shù)關(guān)系：平方關(guān)系： 商的關(guān)系： 典例分析：一、同角

2、三角函數(shù)關(guān)系的應(yīng)用例1已知是三角形的內(nèi)角，若，求的值分析：先求出的值，聯(lián)立方程組求解解：由兩邊平方，得，即又是三角形的內(nèi)角，由，又，得聯(lián)立方程組，解得，得點(diǎn)評(píng)：由于，因此式子，三者之間有密切的聯(lián)系，知其一，必能求其二二、三角函數(shù)的誘導(dǎo)公式1、三角函數(shù)式的化簡(jiǎn)例2已知，求，的值分析：利用誘導(dǎo)公式結(jié)合同角關(guān)系，求值解：由，得，是第二，三象限角若是第二象限角，則，；若是第三象限角，則，點(diǎn)評(píng)：若已知正弦，余弦，正切的某一三角函數(shù)值，但沒有確定角所在的象限，可按角的象限進(jìn)行分類，做到不漏不重復(fù)2、三角函數(shù)的求值例3 （1）已知，且，求的值（2）已知，求的值解：（1）由，得原式=（2），3、誘導(dǎo)公式在三角

3、形中的應(yīng)用例4在abc中，若 求abc的三內(nèi)角。解答：由已知得，化簡(jiǎn)得即（1）當(dāng)時(shí)，又a、b是三角形內(nèi)角，（2）當(dāng)，又a、b是三角形內(nèi)角，不合題意。綜上知，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 has been named at full-back but is still recovering from a knee injury a

4、ggravated 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 hayne is the competitions top try scorer with nine, closely followed by t

5、uivasa-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 offloads - has the chance of becoming the first player to win the world cup

6、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-based webb, the head of fifas anti-racism taskforce, is in london for the

7、 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 how he felt and i would like to speak to him first to find out what his

8、 experience was.uefa 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 immediate investigation into the referees actions.cska said they were surprised and disap

9、pointed 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 sunda.the weather plays an important role in this mission. starting at the ground, con

10、ditions 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) where our day-to-day weather lives. it will climb higher than the tip of mount ev

11、erest (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),e can expect a lot of turbulence.the balloon will slowly drift to the edge of spa

12、ce 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 mistake against the kiwis in manchester.five years ago they cruised through to the final

13、 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 been impressed by the kangaroos focus in their games since then.they have been co

14、ncentrating 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 goes unnoticed in the stands but not by your team-mates.it is as though their enti

15、re 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 expe