Well, the way we denote it is the definite integral from 0 to pi over 2 of cosine of x dx. And all this is is kind of reminiscent of taking a sum of a bunch of super thin rectangles with width dx and height f of x for each of those rectangles. And then you take an infinite number of those infinitely thin rectangles. And that's kind of what this notation is trying to depict. But we know how to do this already. The second fundamental theorem of calculus helps us. We just have to figure out what the antiderivative of cosine of x is or what an antiderivative of cosine of x is evaluated at pi over 2.