1.0 milliseconds -- cycle time for frequency 1 kHz
1 ms -- duration of light for typical photo flash strobe
2.27 ms -- cycle time for the A above middle C in music (440 Hz). If an electric tuning device for musical instruments generates just one tone, this is probably that tone.
... 2, the element 2a is zero and it is impossible to divide by it.)
The symbol
<math>\pm \sqrt {b^2-4ac}</math>
in the formula should be understood as ...