What we're going to do in this video is think about limits involving trigonometric functions. So let's just start with a fairly straightforward one. Let's find the limit as x approaches pi of sine of x. Pause the video and see if you can figure this out. Well, with both sine of x and cosine of x, they're defined for all real numbers, so their domain is all real numbers. You can put any real number in here for x and it will give you an output. It is defined.