x=π/12,y=0则局猜枝tan(π/6+a)=0π/6+a=kπa=kπ-π/兆散6则桐敏k=0,a=-π/6
tan在kπ处取0,k是整数2*π/拆绝12+α=kπα=kπ-π/6当k取0 时α= -π/6下面四个尺梁选项旅困姿中只能选 -π/6