Sorry I'm a bit confuse, are you allow to use Pythagoras in a non right angled triangle?
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$\begingroup$The Pythagorean theorem is a restriction of the law of cosines. Given triangle ABC with sides $a,b,c$ opposite the corresponding angles we have $$a^2=b^2+c^2-2bc\cos A$$ As $\cos 90^\circ=0$ the last term drops out in a right triangle.
$\endgroup$ 2 $\begingroup$No, you can't.
If that were the case, then an equilateral triangle with sides $1, 1, 1$ would have $1^2 = 1^2 + 1^2$, which is not true.
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