写出角a的集合.(1)sina>=根3/2 (2)cosa,=--1/2

题目

写出角a的集合.(1)sina>=根3/2 (2)cosa,=--1/2

答案

sina>=根3/2=sin(π/3)=sin(2π/3)
所以{a|2kπ+π/3<=a<=2kπ+2π/3,k∈Z}
cosa=-1/2=cos(2π/3)=cos(-2π/3)
所以
{2kπ+2π/3,2kπ-2π/3,k∈Z}