For any triangle, the sum of the lengths of any two sides must be greater than or equal to the length of the remaining side.[br]When entering [code]LocusEquation[a+b==c,A][/code] this statement can be doubted. But GeoGebra returns the line [i]BC[/i] which means that point [i]A[/i] must lie on [i]BC[/i] in order to satisfy [i]a[/i]+[i]b[/i]=[i]c[/i]. This actually means that the triangle inequality is true, because in GeoGebra's answer the triangle must be degenerate.