1. The problem statement, all variables and given/known data Triangle ABC have side AB = 10 cm, AC=BC = 13cm, so sin (A-C) is... 2. Relevant Equations sin (A-C) = sin A cos C - cos A sin C 3. The attempt at a solution I see that the triangle can be split into two right-angle triangles. But, sin (A-C) ?? How to get that?