作业帮2(sinπ/5)*(cos3π/5)化简如题
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/10 21:36:34
2(sinπ/5)*(cos3π/5)化简如题
2(sinπ/5)*(cos3π/5)化简
如题
2(sinπ/5)*(cos3π/5)化简如题
2(sinπ/5)*(cos3π/5)=-2(sinπ/5)*(cos2π/5)=-[2(sinπ/5)*(cosπ/5)*(cos2π/5)]/(cosπ/5)=-[2(sin2π/5)*(cos2π/5)]/(2cosπ/5)=-(sin4π/5)/(2cosπ/5)=-1/2* tanπ/5