tan
tan
tanCAB = 1/2,tanDAB = 4/3,tanDCB = -4/3,tanACM = 2,CM-AM垂直,CM/AM = 1/2,AMCD面积 = 1/2 (AM+CD)*CM = 7,ACM-CBM-ABC相似,AMCD为直角梯形
tan
tan
tanCAB = 1/2,tanDAB = 4/3,tanDCB = -4/3,tanACM = 2,CM-AM垂直,CM/AM = 1/2,AMCD面积 = 1/2 (AM+CD)*CM = 7,ACM-CBM-ABC相似,AMCD为直角梯形