x∈[-π /3,π /3]
2xE[-2π /3,2π /3]
2x+π /3E[-π /3,π ]
cos(2x+π /3)E[cosπ,cos0]
cos(2x+π/3)E[-1,1]
-2cos(2x+π/3)E[-2,2]
3-2cos(2x+π/3)E[1,5]
yE[1,5]