π ∫ tan² x/3 dx 0
and d(tanA)/dA = sec^2 A so ∫ tan² x/3 dx = ∫ sec^2 (x/3) - 1 dx form 0 to π = [3 tan (x/3) - x] from 0 to π = 3tan π/3 - π -(3tan 0 - 0) = 3 √3 - π
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