【课题背景】在如今减负的背景下,如何优化教学过程,减负增效、提高教学质量是目前困扰教师的疑难问题,寻求科学有效的方法解决这一问题成为许多学校研究的重要课题.问题串的设计作为教学设计中的一个重点受到我校教师的广泛关注,通过问题串的设计,不断激发学生学习的兴趣,帮助学生思维向纵深推进,充分体现了新课程所倡导的学生学习的主动性和探究性.【教材分析】《余弦定理》是普通高中课程标准实验教科书 【Background】 How to optimize the teaching process, reduce the negative pressure and increase the efficiency and improve the teaching quality are the difficult problems which plagued the teachers in the context of reducing the burden nowadays, and finding a scientific and effective way to solve this problem has become an important issue for many schools. As a key point in teaching design, the design of our school is widely concerned by the teachers in our school. Through the design of the string of questions, we can stimulate the students’ interest in learning and help the students to further their thinking. This fully embodies the initiative of the students in the new curriculum And inquiry. 【Textbook Analysis】 “cosine theorem” is an ordinary high school curriculum standard experimental textbook