G.350 prime numbers more — Heath
IX.20
Prime numbers are more than any assigned multitude of prime numbers.
Let A, B, C be the assigned prime numbers ;
I say that there are more prime numbers than A, B, C.
For let the least number measured by A, B, C be taken, and let it be / D E / ; let the unit / D F / be added to / D E /.
Then / E F / is either prime or not.
First, let it be prime ;
then the prime numbers A, B, C, / E F / have been found which are more than A, B, C.
Next, let / E F / not be prime ;
[G.287]therefore it is measured by some prime number.
Let it be measured by the prime number G.
I say that G is not the same with any of the numbers A, B, C.
For, if possible, let it be so.
Now A, B, C measure / D E / ;
therefore G also will measure / D E /.
But it also measures / E F /.
Therefore G, being a number, will measure the remainder, the unit / D F / : which is absurd.
Therefore G is not the same with any one of the numbers A, B, C.
And by hypothesis it is prime.
Therefore the prime numbers A, B, C, G have been found which are more than the assigned multitude of A, B, C.
Q. E. D.
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