y=[cos(x+2π/5)-1]/sin(x+2π/5)=[1-2sin²(x/2+π/5)-1]/[2sin(x/2+π/5)cos(x/2+π/5)] =-sin(x/2+π/5)/cos(x/2+π/5) =-tan(x/2+π/5)定义域sin(x/2+π/5)≠0,cos(x/2+π/5)≠0∴x/2+π/5≠kπ/2,k∈Z由 ...