And this is useful because this is defined for negative values, not just positive values. The natural log of x is only defined for positive values of x. But when you take the absolute value, now it could be negative or positive values of x. And it works, the derivative of this is indeed one over x. Now it's not so relevant here because our bounds of integration are both positive. But if both of our bounds of integration were negative, you could still do this by just reminding yourself that this is the natural log of absolute value of x. So this, we could say, is plus the natural log of the absolute value of x.