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1、Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd. DABE1.6m20m42C引例引例 升国旗时,小明站在操场上离国旗升国旗时,小明站在操场上离国旗20m处行注目礼。处行注目礼。当国旗升至顶端
2、时,小明看国旗视线的仰角为当国旗升至顶端时,小明看国旗视线的仰角为42(如图(如图所示),若小明双眼离地面所示),若小明双眼离地面1.60m,你能帮助小明求出旗,你能帮助小明求出旗杆杆AB的高度吗?的高度吗?这里的这里的tan42是多少呢?是多少呢?Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Clien
3、t Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd. 前面我们学习了前面我们学习了特殊角特殊角304560的三角的三角函数值,一些函数值,一些非特殊角非特殊角(如如175689等等)的三的三角函数值又怎么求呢?角函数值又怎么求呢? 这一节课我们就学习这一节课我们就学习借助计算器借助计算器来完来完成这个任务成这个任务.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.
4、Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.按键顺序按键顺序 显示结果显示结果sin18rldmm89898891、用科学计算器求一般锐角的三角函数值:、用科学计算器求一般锐角的三角函数值:(1)我们要用到科学计算器中的)我们要用到科学计算器中的键:键:sincostan(2)按键顺序)按键顺序如果锐角恰是整数度数时,以如果锐角恰是整数度数时,以“求求sin18”为例,按键顺序如下:为例,按键顺序如下:sin18
5、sin180.309 016 994 sin18= 0.309 016 9940.31Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.1、用科学计算器求一般锐角的三角函数值:、用科学计算器求一
6、般锐角的三角函数值:如果锐角的度数是度、分形式时,以如果锐角的度数是度、分形式时,以“求求tan3036”为例,按键顺序如下:为例,按键顺序如下:方法一:方法一:按键顺序按键顺序显示结果显示结果tan3036tan3036tan30360.591 398 351 tan3036 = 0.591 398 3510.59方法二:方法二:先转化,先转化, 3036 =30.6,后仿照后仿照 sin18的求法。的求法。如果锐角的度数是度、分、秒形式时,依照上面的如果锐角的度数是度、分、秒形式时,依照上面的方法一求解。方法一求解。Evaluation only.Created with Aspose.S
7、lides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.(3)完成引例中的求解:)完成引例中的求解:tan2042 +1.619.608 080 89 AB = 19.608 080 8919.61m即旗杆的高度是即旗杆的高度是19.61m.Evaluation only.
8、Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.练习练习:使用计算器求下列锐角的三角函数值使用计算器求下列锐角的三角函数值.(精确到(精确到0.01)(1)sin20,cos70; sin35,cos55; sin1532,
9、cos7428;(2)tan38,tan802543;(3)sin15+cos61tan76.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.按键的顺序按键的顺序显示结果显示结果SHIFT20
10、917.301507834sin7= 已知三角函数值求角度,要用到已知三角函数值求角度,要用到sin,Cos,tan的的第二功能键第二功能键“sin Cos,tan”键例如:已知键例如:已知sin0.2974,0.2974,求锐角求锐角按健顺序为:按健顺序为:如果再按如果再按“度分秒健度分秒健”就换算成度分就换算成度分秒,秒,即即 17o185.43”2、已知锐角的三角函数值,求锐角的度数:、已知锐角的三角函数值,求锐角的度数:Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyr
11、ight 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.例例 根据下面的条件,求锐角根据下面的条件,求锐角的大小(精确到的大小(精确到1 1)(1)sin=0.4511;(;(2)cos=0.7857; (3) tan=1.4036. w按键盘顺序如下按键盘顺序如下: :按键的顺序按键的顺序显示结果显示结果26260 048485151”0.sin115=4SHIF
12、T即即 2604851”Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.驶向胜利驶向胜利的彼岸的彼岸练习练习:1、已知下列锐角三角函数值,用计算、已知下列锐角三角函数值,用计算器求其相应的锐角
13、:器求其相应的锐角:(1)sinA=0.627 5,sinB=0.054 7;(2)cosA=0.625 2,cosB=0.165 9;(3)tanA=4.842 5,tanB=0.881 6.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright
14、2004-2011 Aspose Pty Ltd.2、已知、已知tanA=3.1748,利用计算器求,利用计算器求锐角锐角A的度数。的度数。(精确到精确到1)答案答案:A7252练习练习:3、已知锐角、已知锐角a的三角函数值,使用计算器求锐角的三角函数值,使用计算器求锐角a(精确(精确到到1)(1)sin a=0.2476;(;(2)cos a=0.4;(;(3)tan a=0.1890. 答案答案: (1)1420;(3)1042.(2)6520;Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.
15、2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.4、一段公路弯道呈弧形,测得弯道、一段公路弯道呈弧形,测得弯道AB两端的距离为两端的距离为200米,米,AB 的半径为的半径为1000米,求弯道的长(精确到米,求弯道的长(精确到0.1米米)ABOREvaluation only.Created with Aspose.Slides for
16、 .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.作业:作业:1、抄写和背诵:各三遍。、抄写和背诵:各三遍。2、基训一课时。、基训一课时。3、预习下一课。、预习下一课。Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Copyright 2004-2011 Aspose Pty Ltd.