Question 1091279
KNOWN sides a, b, c;
Unknown angle measure opposite of each of those sides, A, B, C;


Find any angle, for example, at point C:
{{{a^2+b^2-2ab*cos(C)=c^2}}}------Law Of Cosines
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{{{a^2+b^2-c^2=2ab*cos(C)}}}
{{{cos(C)=(a^2+b^2-c^2)/(2ab)}}}-----and then inverse cosine to find angle at C.


More than one way, to continue.