Well, the blue graph is gonna look like this one right over here. And if it was cosine of x up here, we can now say that this is equal to, y is equal to cosine of x plus pi over two. This is the blue graph, cosine of x, shifted to the left by pi over two. And this is y is equal to sine of x plus pi over two. Now the visual argument is, all I did is I shifted both of these graphs to the left by pi over two. So it should still be the case that the derivative of the red graph is the blue graph. So we should still be able to say that the derivative with respect to x of the red graph, sine of x plus pi over two, that that is equal to the blue graph.