A 2π periodic function \(f\left( x \right) = \left\{ {\begin{array}{*{20}{c}} {x,}&{ - \pi < x < 0}\\ { - x,}&{0 < x < \pi } \end{array}} \right.\) is expanded as a Fourier series of the form \({a_0} + \mathop \sum \limits_{n = 1}^\infty {a_n}\cos \left( {nx} \right) + \mathop \sum \limits_{n = 1}^\infty {b_n}{\rm{sin}}\left( {nx} \right)\)
Which of the following is TRUE?1
a0 ≠ 0, bn = 0
2
a0 ≠ 0, bn ≠ 0
3
a0 = 0, bn = 0
4
a0 = 0, bn ≠ 0