Complex Imaginary Vol I problem 75 asks to find the ripple factor of a 3 phase DC rectifier. The formula they use for the solution is r = (Vrms/Vavg) * 100 (actually, they write Vac for Vrms and Vdc for Vavg) for a ripple factor of 103%. But I thought ripple factor r = sqrt((Vrms/Vavg)2-1) * 100, a formula which they actually use in Vol IV problem 25. So why the different formula in the first problem?