how do I get angle of a triangle not right angled when I know three sides

\(Cosine \ set\)

\(a^2=b^2+c^2-2bc\ cos\alpha\)

\(\alpha=arccos\frac{b^2+c^2-a^2}{2bc}\)

\(\beta=arccos\frac{a^2+c^2-b^2}{2ac}\)

\(\gamma=arccos\frac{a^2+b^2-c^2}{2ab}\)

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