Yes, another thread... lab due tomorrow :tongue2: We take the integral of the function f(t) times one of the components: integral(0->T) of [a0 + sigma(n=1->N) acos(nwt) + bsin(nwt)]sin(nwt) Now, in order to evaluate this is it correct to say we multiple sin(nwt) through then take the integral of each term seperately, and given the orthogal properties of sine/cosine we say the first two terms are 0 but the bsin^2(nwt) becomes bT/2? I guess I should say what's confusing me: the sigma; because shouldn't the acos and bsin be in brackets and then we couldn't isolate the terms in the same way. Is it because this is true?: integral(0->T) of [a0 + sigma(n=1->N) acos(nwt) + sigma(n=1->N) bsin(nwt)]sin(nwt) and then we can multiply through by sin(nwt) to get the three terms? Sorry for the shotty math.