Page:Calculus Made Easy.pdf/22

 integral of.” Now any fool can see that if $$x$$ is considered as made up of a lot of little bits, each of which is called $$dx$$, if you add them all up together you get the sum of all the $$dx$$’s, (which is the same thing as the whole of $$x$$). The word “integral” simply means “the whole.” If you think of the duration of time for one hour, you may (if you like) think of it as cut up into $$3600$$ little bits called seconds. The whole of the $$3600$$ little bits added up together make one hour.

When you see an expression that begins with this terrifying symbol, you will henceforth know that it is put there merely to give you instructions that you are now to perform the operation (if you can) of totalling up all the little bits that are indicated by the symbols that follow.

That’s all.