The general solutions for the harmonic oscillator differential equation fall into four general categories: 1) Undamped: [math]x(t) = Ae^{i\omega t}[/math] This is a free-running sinusoidal oscillation that doesn't change over time.
Key Facts. 1  Itâs normal to have mild cramps during your period. 2  Menstrual cramps often start 1-2 days after your period begins. 3  If your cramps donât get better with over-the-counter medicine, you should see your health care provider.
Premenstrual cramping (before your period starts) usually happens a day or two before your period begins and stops after the first day or two of your period. Your hormones that have built up the lining in your uterus start to go down and other hormones start to prepare for your period to come.