For example, suppose you wanted to take the square root of 85. You can observe that 9 squared is 81, so the answer is sort of 9, right? But that’s off by 4 (85-81=4). So you take that number and ...

Then there was root-mean-square (RMS) voltage. For those nice sine waves, you took the peak voltage and divided by the square root of two, 1.414 or so. You know that kid in the front of the class?