Now the shapes have been sorted using a Venn diagram. What is special about the square? It is a quadrilateral and a regular shape. Can you guess why the right-angled triangle in the outside set?

A Venn diagram captioned: "In a survey of 250 European travelers, 93 have traveled to Africa, 155 have traveled to Asia, and 70 have traveled to both of these continents, as illustrated in the Venn ...

When two-dimensional electron systems are subjected to magnetic fields at low temperatures, they can exhibit interesting ...

But the ancient Greeks certainly had numbers. In fact, they had what was in some ways a much more elegant system than the ...