And what is cosine of x plus pi over two? Well, once again, from our trig identities, we know that that is the exact same thing as negative sine of x. So there you have it, the visual argument. Just start with this knowledge, shift both of these graphs to the left by pi over two. It should still be true that the derivative with respect to x of sine of x plus pi over two is equal to cosine of x plus pi over two. And this is the same thing as saying what we have right over here. So now we should feel pretty good.