In Donald Trump’s imaginary world, Americans can’t venture out to buy a loaf of bread without getting shot, mugged or raped. Immigrants in a small Ohio town eat their neighbors’ cats and dogs.

Mathematicians once turned up their noses at imaginary numbers. But complex analysis actually simplifies math and physics.

MARCUS DU SAUTOY:'As strange as it may seem, 'that's because even the so-called imaginary bits of mathematics 'can be used to explain, control and accurately predict the real world.' Starting with ...