The three numbers: 12, 35, 37
Applying these number to Pythagorean theorem…
a2+b2=c2
So,
12^2+35^2=37^2
144+1225=1369
1369=1369
As you can see both are equal (1369=1369), so we have a right angle triangle. If both sides are not equal then it is not classified as a right angle triangle.
Of your numbers listed, 29 and 41 are the lengths of the hypotenuse of a Pythagorean triple.
Those triples are
(20, 21, 29)
(9, 40, 41)
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The On-Line Encyclopedia of Integer Sequences (OEIS) lists the hypotenuses of primitive triples as sequence number A020882.
sec (theta) = 
sin(theta)=
cot(theta)=