利用三角函数的定义求7π/6的三个函数值

∵7π/6=π+π/6
sin7π/6=sin(π+π/6)=-sinπ/6=-1/2
cos7π/6=cos(π+π/6)=-cosπ/6=-√3/2
tg7π/6=tg(π+π/6)=tgπ/6=√3/3
方法二：在单位圆上，半径=1转到7π/6时，半径的端点（-√3/2，-1/2）
sin7π/6=对边/斜边=-1/2
cos7π/6=邻边/斜边=-√3/2
tg7π/6=对边/邻边=√3/3