And if we were to graph all of the points x and y that satisfy this relationship, we get a unit circle like this. And what I'm curious about in this video is how we can figure out the slope of the tangent line at any point of this unit circle. And what immediately might be jumping out in your brain is well, a circle defined this way, this isn't a function. It's not y explicitly defined as a function of x. For any x value, you actually have two possible y's that satisfy this relationship right over here. So you might be tempted to maybe split this up into two separate functions of x. You could say y is equal to the positive square root of one minus x squared.