Why do I think this is useful? Well, let's think about what happens when I take the derivative of both sides using the chain rule. On the left-hand side, I am going to have an x prime of t, and then that's going to be equal to, what do I end up on the right-hand side? Well, using the chain rule, first I'll take the derivative with respect to theta, and so that's just going to be negative 20 sine of theta of t, and then I need to multiply that times theta prime of t. So, what I could do is say, hey, look, at t sub zero, I know what x prime of t is, I could try to figure out what sine of theta of t is, and then I'll just solve for this right over there. So, let's do that. So, at t sub zero, so at t is equal to t sub zero, t sub zero, what we're gonna have, x prime of t, well, that's at every time, it's three meters per minute, we'll assume that our rates are in meters per minute, and just our values are in meters when we're talking about distance, and our angles are in radians. So, this is going to be equal to three is equal to negative 20 times sine of theta of t times the derivative of theta with respect to time.