tan(3π+α)=√3,则tanα=√3 [说明：正切函数的周期是π]
α∈﹙0,π/2﹚
α=π/3
cos﹙π＋α﹚
=-cosα
=-cosπ/3
=-1/2
sin﹙3π＋α﹚
=-sinα
=-sinπ/3
=-√3 /2