I've been going over the basics reading the Art of Electronics (3rd ed.) by Horowitz & Hill. I am currently reading about the shortcomings of the single-stage grounded-emitter amplifier. Precisely, their non-linearity. I'm kinda lost in that part where the authors say (on p. 94):
Because this represents the extreme variation of gain (i.e., at the peaks of the swing), the overall waveform "distortion" (usually stated as the amplitude of the residual waveform after subtraction of the strictly linear component) will be smaller by roughly a factor of 3.
Where does that 3 come from? How did they derive it?