1. The problem is about understanding how to determine where each period starts or ends in a periodic function. 2. A periodic function repeats its values in regular intervals called periods. 3. The period $T$ is the length of one complete cycle of the function. 4. To find where each period starts or ends, you identify points where the function repeats its value and pattern. 5. Mathematically, if $f(x)$ is periodic with period $T$, then $f(x) = f(x + T)$ for all $x$. 6. This means the function's graph from $x = a$ to $x = a + T$ looks exactly the same as from $x = a + T$ to $x = a + 2T$, and so on. 7. Usually, the period starts at a point where the function has a specific feature like a peak, trough, or zero crossing that repeats. 8. For example, for $y = \sin x$, the period is $2\pi$, and each period starts at $x = 0, 2\pi, 4\pi, \ldots$ where the sine wave repeats. 9. To summarize, the start and end of each period are separated by the period length $T$, and you find them by locating repeating points in the function's behavior.