正弦定理解三角形问题(2)已知两边和其中一边的对角,求其他角和边制作人:张艳周南雨花中学正弦定理在一个三角形中,各边和它所对角的正弦的比相等.sinsinsinabcABC即01616303abA例1、已知,,,解三角形.例1、已知a=16,b=,A=30°,解三角形.解:由正弦定理231630sin316sinsinaAbB所以B=60°,或B=120°163B16300ABC16sinsinabAB00,,0180abABB且163000(1)60,180()90CAB当Bsin32sinAaCc000(2)120,180()30CAB当Bsin16.sinAaCc注:三角形中角的正弦值小于1时,角可能有两解得0,2,45,,,.ABCbACc例2、在中,a=2求BPPT模板下载:www.1ppt.com/moban/行业PPT模板:www.1ppt.com/hangye/节日PPT模板:www.1ppt.com/jieri/PPT素材下载:www.1ppt.com/sucai/PPT背景图片:www.1ppt.com/beijing/PPT图表下载:www.1ppt.com/tubiao/优秀PPT下载:www.1ppt.com/xiazai/PPT教程:www.1ppt.com/powerpoint/Word教程:www.1ppt.com/word/Excel教程:www.1ppt.com/excel/资料下载:www.1ppt.com/ziliao/PPT课件下载:www.1ppt.com/kejian/范文下载:www.1ppt.com/fanwen/试卷下载:www.1ppt.com/shiti/教案下载:www.1ppt.com/jiaoan/0,2,45,,,.ABCbACc例2、在中,a=2求B解:由正弦定理sinsinabAB22sin12sin22bABa得00,,0180abABB且00030180()105BCAB,sin26231sin422aCcA