[课件28.3.ppt

* * * * * Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 两块三角尺中有几个不同的锐角？分别求出这几个锐角的正弦值、余弦值和正切值． 30° 60° 45° 45° Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 30°、45°、60°角的正弦值、余弦值和正切值如下表： 锐角a 三角函数 sin a cos a tan a 30° 45° 60° Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例3 求下列各式的值： （1）cos260°＋sin260° （2） (3)tan450.sin450-4sin300.cos450+cos2300 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 求下列各式的值： （1）1－2 sin30°cos30° （2）3tan30°－tan45°+2sin60° （3） 练习 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例4 （1）如图，在Rt△ABC中，∠C＝90°， ， 求∠A的度数． A B C Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. （2）如图，已知圆锥的高AO等于圆锥的底面半径OB的 倍，求 a ． A B O Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 练习2. 在Rt△ABC中，∠C＝90°， 求∠A、∠B的度数． B A C Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. A B C D 3. 如图,在RT△ABC中,∠ACB=900,CD⊥AB于D,已知∠B=300,计算tan∠ACD+sin∠BCD的值. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. C A B 4. 如图,在RT△ABC中,∠C=900,若tanA+tanB=4,S△ABC=8.求斜边AB的长. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. A B C D 5 如图,△ABC中,∠C=900,BD平分∠ABC,BC=12,BD= ,求∠A的度数及AD的长. 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 w