角的比较与运算1学习资料.ppt

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1、角的比较与运算1自学指导认真看课本（P134-P136练习前）注意：1、角的比较有哪些方法？回答“思考”和“探究”中的问题。2、理解角平分线的概念，会表示这三个角的关系。3、类比线段的和、差运算，掌握角的运算，注意例题解题的格式和步骤。7分钟后，比谁能正确的做出与例题类似的习题。交流思考借助手中的一副三角板，你能画出15°、75°的角吗？你还可以画出其它角吗？你发现有什么规律？（角的度数在0°到180°之间）可以画出15°，30°，45°，60°，75°，90°，105°，120°，135°，150°，165°，180°规律：

2、这些度数都是15的倍数B做一做OCA从一个角的顶点出发，把这个角分成相等的两个角的射线叫做这个角的角平分线。在一张纸上画出一个角∠AOC并剪下，将这个角对折，使其两边重合，折痕记作OB，它与角两边所成的两个角的大小有什么关系？OB平分AOC（已知）AOB=BOC=1/2AOC或AOC=2AOB=2BOC（角平分线定义）ABCDO如图∠AOB＝∠BOC＝∠COD，则OB是的平分线，＝∠AOC，＝∠BOD∠BOC＝＝`AOCBOCBOCAODBODAOD此时OB、OC叫∠AOD的三等分线练一练检测题P136练习1.2.3题shop

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