Answer: Right triangle
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Work Shown:
Let a,b,c be the sides of a triangle such that a < b < c. In our case,
a = 39
b = 80
c = 89
which means,
a^2+b^2 = 39^2+80^2 = 7921
and
c^2 = 89^2 = 7921
Because both result in the same value (7921), we know,
39^2+80^2 = 89^2 is a true equation
a^2+b^2 = c^2 for the specified a,b,c values above
By the converse of the pythagorean theorem, this proves the three sides form a right triangle.