The maximum value of cos2(π3−x)−cos2(π3+x) is
- √32
12
√32
32
cos2(π3−x) - cos2(π3+x)
= {cos(π3−x)+cos(π3+x)} {cos(π3−x)−cos(π3+x)}
= {2cosπ3cosx} {2sinπ3sinx}
= sin 2π3 sin 2x = √32 sin 2x
Its maximum value is √32, {- 1 ≤ sin 2x ≤ 1}.