| > f(x) = 3x [-2, 2]
f(x)=3x (-2≦x<2), f(x)=f(x+4n) の意味なら、
a[n]=0 b[n]=(2/T)∫[-2〜2] f(x)sin(2πnx/T)dt=(2/4)∫[-2〜2]3xsin(2πnx/4)dx =3∫[0〜2]xsin(πnx/2)dx=3[-{2/(πn)}xcos(πnx/2)][0〜2] +3{2/(πn)}∫[0〜2]cos(πnx/2)dx =-12/(πn)cos(πn)+[{12/(πn)^2}sin(πnx/2)][0〜2]= =(-1)^(n+1)12/(πn)
f(x)=Σ[n=1〜∞]{(-1)^(n+1)12/(πn)}sin(πnx/2)
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