Problem 9.3 a) Find the Fourier series coefficients for the forcing function in the plot below. You may use software to help you evaluate the integrals but you may not just plug the function into Mathematica's FourierTrigSeries or equivalent. b) Write the 2nd-order series in expanded form. C) Plot 8 periods of the original function, the 2"d-order Fourier series, and the 6 -order Fourier series. Hint: The Matlab functions i f and mod may be useful. 120 n odd Answer: a) do = 20, an = TT2n2 72 Cos(20nt) - 30 120 ,bn = 0b) f (t) = 20 + 120 72 COS (40rt) n even IT 2n2 30 -12000t 2+30 -12000t 2+2400t-90 20 Force (N 10 O 0 0.05 0.1 0.15 0.2 0.25 0.3 Time (s)