If this is a right triangle, then the Pythagorean theorem has to be valid.
This means that the sum of the squares of the legs has to be equal to the square of the hypotenuse (NOTE: we can identify the potential hypotenuse by finding the side with the most length).
Then, we calculate:
[tex]\begin{gathered} 12^2+16^2=20^2 \\ 144+256=400 \\ 400=400\longrightarrow\text{True} \end{gathered}[/tex]
As the Pythagorean theorem is valid for this side's lengths, we know that this triangle is a right triangle.
Answer: Yes.
