2cos(p-2x)>1
cos(pi - 2x) > 1/2
2pk - arccos1/2 < pi - 2x < 2pk<span> + arccos1/2, k∈Z
2pk - pi/3 < pi - 2x < 2pk + pi/3, k∈Z<br>2pk - pi/3 -pi < - 2x < 2pk + pi/3 - pi, k∈Z<br>2pk - 4pi/3 < - 2x < 2pk - 2pi/3, k∈Z<br>-pk + 2pi/3 > x > -pk + pi/3, k∈Z
pi/3 - pik < x < 2pi/3 - pik, k∈Z