https://mathshistory.st-andrews.ac.uk/HistTopics/Prime_numbe...
This is one of the first proofs known which uses the method of contradiction to establish a result.
https://en.wikipedia.org/wiki/Euclid%27s_theorem
Euclid is often erroneously reported to have proved this result by contradiction beginning with the assumption that the finite set initially considered contains all prime numbers, though it is actually a proof by cases, a direct proof method.
reply
https://mathshistory.st-andrews.ac.uk/HistTopics/Prime_numbe...
This is one of the first proofs known which uses the method of contradiction to establish a result.
https://en.wikipedia.org/wiki/Euclid%27s_theorem
Euclid is often erroneously reported to have proved this result by contradiction beginning with the assumption that the finite set initially considered contains all prime numbers, though it is actually a proof by cases, a direct proof method.
reply