You've got to ask yourself, let the time it takes to do a full circle, that's the time period, do a full circle.

你已经问你自己了,留足够的时间让它运动一整圈,那就是运动整个圆周的时间周期

耶鲁公开课 - 基础物理课程节选

You can take one full circle divide by the time and you will get this.

你可以先转一整圈,再除以时间就得到这个

耶鲁公开课 - 基础物理课程节选