三角函数讲义2

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1、专业好文档第2讲 同角三角函数的基本关系与诱导公式1、 考纲点击（1）平方关系：（2）商数关系：（3）能利用单位圆中的三角函数线推导出的正弦、余弦、正切的诱导公式。2、热点提示（1）利用诱导公式求值或化简三角函数是考查重点。（2）同角三角函数关系式用来化简，求值是高考热点。（3）主要以选择题、填空题的形式考查。知识整合：1：熟记特殊角的三角函数值：角030456090120135150180弧度数正弦余弦正切2：诱导公式：（填表）正弦余弦可概括为：奇变偶不变，符号看象限如：sin390= cos（45）= tan（= 3、同角三角函数关系：平方关系： 商的关系： 典例分析：一、同角三角函数关系

2、的应用例1已知是三角形的内角，若，求的值分析：先求出的值，联立方程组求解解：由两边平方，得，即又是三角形的内角，由，又，得联立方程组，解得，得点评：由于，因此式子，三者之间有密切的联系，知其一，必能求其二二、三角函数的诱导公式1、三角函数式的化简例2已知，求，的值分析：利用诱导公式结合同角关系，求值解：由，得，是第二，三象限角若是第二象限角，则，；若是第三象限角，则，点评：若已知正弦，余弦，正切的某一三角函数值，但没有确定角所在的象限，可按角的象限进行分类，做到不漏不重复2、三角函数的求值例3 （1）已知，且，求的值（2）已知，求的值解：（1）由，得原式=（2），3、诱导公式在三角形中的应用例

3、4在ABC中，若 求ABC的三内角。解答：由已知得，化简得即（1）当时，又A、B是三角形内角，（2）当，又A、B是三角形内角，不合题意。综上知，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 aggrava

4、ted 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 Tuivasa

5、-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 in bot

6、h 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 Footb

7、all 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 exper

8、ience 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 disappointe

9、d 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, condition

10、s 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 Everest

11、(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 space at

12、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 and s

13、o 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 concentr

14、ating 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 entire tou

15、rnament 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 experienced but winning a dramatic match like their semi-final against England will do wonders for their confidence.They defeated Australia in the Four Nations final in 2010 and the last World Cup, and know they can rise to the big occasion.