Basic Examples 
(2)
 

A 3-4-5 triangle exists:
In[1]:=
[◼]
TriangleEdgesQ
[{3,4,5}]
Out[1]=
True
———
A 3-4-7 triangle does not exist:
In[2]:=
[◼]
TriangleEdgesQ
[{3,4,7}]
Out[2]=
False