R[a,b] is remann integral Solution Do you know if f+g is also Riemann integrable? Because then we know from your previous question that (f+g)^2 is also Riemann integrable implying (f+g)^2 = f^2 + g^2 + 2fg => fg = -1/2(f^2 + g^2 - (f+g)^2) Is Riemann integrable (by composition and addition of Riemann integrability preserves it)..