早教吧 育儿知识 作业答案 考试题库 百科 知识分享

已知cos(x-四分之派)=五分之三,则cosx=如题

题目详情
已知cos(x-四分之派)=五分之三,则cosx =
如题
▼优质解答
答案和解析
cos(x-π/4) = 3/5cosxcosπ/4+sinxsinπ/4 = 3/5cosx+sinx = 3√2/5sinx = 3√2/5-cosxsin²x = (3√2/5-cosx)²1-cos²x = 18/25-6√2/5cosx+cos²xcos²x-3√2/5cosx-7/50 = 0(cosx+√2/10)(...
看了已知cos(x-四分之派)=五...的网友还看了以下: