分类：教育/科学-学习帮助
问题：三角函数cos(a
c(a-pai/6)+sina=4√3/5,则sin(a+7pai/6)=? 做不来啊
回答：cos(a-π/6)+sina
=cosa*cosπ/6+sina*sinπ/6+sina
=√3/2*cosa+3/2*sina
=√3sin(a+π/6)
sin(a+π/6)=4/5
sin(a+7π/6)=-sin(a+π/6)=-4/5