the difference between the proof in time of Euclid and the proof in nineteenth and twentieth centuries

Question

What is the difference between a proof at the time of Euclid and proof in the nineteenth and twentieth centuries?

Thanks for your help

Answer 1

If you read Euclids "The elements" Euclid was mostly busy with (geometric constructions) while now it is much more algebra, deduction and deduction from first principles(axioms)

but even this is a bit a caricature, euclid also used reductio ad absurdum. (proof that something isn't possible)

But still for Euclid it looks enough that when it looks correct on paper it is correct enough, while now you need to proof that two circles intersect at a point, showing that it looks like that they do is not enough.