知识点:在直角三角形中,如果一个锐角等于30°,那么它所对的直角边等于斜边的一半。巩固习题:(每道题目都要画图以帮助自己分析)1.在ABCRt中,90C,cmABA10,30,求?BC2.在ABCRt中,90C,cmABA20,30,求?BC3.在ABCRt中,90C,cmABA40,30,求?BC4.在ABCRt中,90C,cmBCA20,30,求?AB5.在ABCRt中,90C,cmBCA15,30,求?AB6.在ABCRt中,90C,cmBCA25,30,求?AB7.在ABCRt中,90C,cmACB25,30,求?AB8.在ABCRt中,90C,cmABB50,30,求?AC