Intervals Other Than [-π,π]
   Intervals Other Than [-π,π] :                   So far we have considered the interval [-π,π] only . It was just a matter of convenience , otherwise any finite interval could have been used . We now show that by effecting certain transformations , any finite interval can be made to correspond to the interval      [-π,π] .        The Interval [0,2π] :                     If f is bounded , integrable and piecewise monotonic in [0,2π] , then the sum of the series                           ∞            1/2 a₀ + Σ (aₙ cos nx + bₙ sin nx)                         n=1                               2π    where aₙ = 1/π ∫ f cos nx dx ,                    ...