The following code may help you to plot the first, 3rd and fifth harmonics of the signal
t = 0:0.1:4*pi;
numTerms = 3;
fourierExpansion = zeros(numTerms, numel(t));
for i=1:numTerms
fourierExpansion(i,:) = (6/((2*i - 1)*pi))*sin((2*i - 1)*t);
end
z = sum(fourierExpansion) + 3/2;
plot(t,[z;fourierExpansion]);
legend('z','b1','b2','b3');
