So the antiderivative of sine of pi x is going to be negative 1 over pi cosine of pi x. And you can verify it for yourself. And you might say, wait, how did you know it was a negative? Well, I put the negative there so that when I take the derivative of the cosine of pi x, I would get a negative sign. But that negative will cancel out the negative to give me a positive here. And you say, why did you put a 1 over pi here? Well, when you take the derivative of this thing using the chain rule, you take the derivative of the pi x, you'll get pi that you would multiply everything by.