A story about a small boy and the integral is uncertain.
When I was a kid, my mother studied as a designer engineer, at that time not autocaders and plotters, all drawn on vatman. And I liked it too, then put a pencil, then an ambulance. I studied science accordingly. Once a fellow student brought to us home his drawing, asked to check for errors. Mom turned on the table, and let’s look, and I approach from the other side, I look at the drawing, and I say, “Mom, there’s not enough arrow at the crane.
(On drawings near the shutter valve, a arrow is needed that shows the direction of rotation when closing). You would see the birth of this student. A 5-year-old boy found a mistake on his course drawing.