Hello,

I am currently reading about the preliminary work used to define the double integral, and there is one thing my author states, whose meaning I am not certain I understand. Here is an excerpt:

"The rectangles lying entirely within $\displaystyle R$ form an inner partition whose norm $\displaystyle || \Delta ||$ is defined as the length of the longest diagonal of the $\displaystyle n$ rectangles."

Could someone possibly explain the meaning of this to me, especially the part about the longest diagonal?

Thank you in advanced!