6 karma · joined March 6, 2017
You could also use the law of cosines to get a triangle's angles pretty easily when you know its edge lengths: https://mathworld.wolfram.com/LawofCosines.html.
To answer the better-specified question we need first to define the real numbers and what it means to multiply two real numbers together. This would be done in a real analysis class, after which one could properly prove that sqrt(2) exists, and understand what the proof actually accomplishes.
I believe that the article poses the problem as whether sqrt(2) exists and not as whether sqrt(2) is a unique real number because the article is meant to appeal to the outsider who wouldn't see the point of the quantification, at least, not before reading the article.