Can I measure a Square-Root sinusoidally Waveform's Frequency Using a Digital Oscilloscope
Nothing ill-defined about that, the frequency is 2Hz. 

Perhaps it is created by a 1 Hz sinusoidal current, but it is doubled.

To read the frequency, note the period from the sweep of 250ms/division- each cycle takes 2 divisions or 500ms so the frequency is 1/0.5 = 2.0 Hz.

You can make your reading of the display a bit more accurate by looking at several cycles, or by changing the sweep to fill more divisions. At higher frequencies your Tek scope will do the calculation for you, but in this case it is too low and it just shows &lt;10 Hz.