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Twice Prime (Posted on 2024-06-03) Difficulty: 3 of 5
(A) Prove that a triangle with integer sides cannot have an area that is prime.

(B) Determine a triangle with rational sides whose area and perimeter are both prime.

No Solution Yet Submitted by K Sengupta    
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Some Thoughts How one might computer search part B Comment 2 of 2 |
Assuming this can be derived from a Heronian triangle.  If we had one with area n^2*p and perimeter n*q for primes p and q then we could scale it down by a factor of n.

A hand search of the smallest triangles given on 
https://en.wikipedia.org/wiki/Heronian_triangle#Properties_of_side_lengths
gives no results.
(But some are close.  There's a pair with A=396=36*11 and p=198=6*33 but of course, 33 is not prime.)

There are some nice parameterizations such as Euler's 
gcd(m,n)=gcd(p,q)=1
Area=mnpq(mq+np)(mp-nq)
perimeter=2mp(mq+np)






  Posted by Jer on 2024-06-03 16:34:55
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