And we're gonna base this argument based on a previous proof we made that the derivative with respect to x of sine of x is equal to cosine of x. So we're gonna assume this over here. I encourage you to watch that video. That's actually a fairly involved proof that proves this. But if we assume this, I'm gonna make a visual argument that this right over here is true, that the derivative with respect to x of cosine of x is negative sine of x. So right over here, we see sine of x in red and we see cosine of x in blue. And we're assuming that this blue graph is showing the derivative, the slope of the tangent line for any x value of the red graph.