So let's write that down. So we know that the tangent, the tangent of theta, tangent of theta is equal to the opposite side, the opposite side is equal to h, is equal to h over the adjacent side, which we know is going to be a fixed 500, is going to be a fixed 500. So there you have a relationship between theta and h. And then to figure out a relationship between theta, d theta, and d h, or d theta, d t, the rate at which theta changes with respect to t, and the rate at which h changes with respect to t, we just have to take the derivative of this, of both sides of this, with respect to t implicitly. So let's do that. And actually, let me move over this h over 500 a little bit. So let me move it over a little bit so I have space to show the derivative operator. So let's write it like that.