FRAC{\cos A}{a}+\frac{\cos B}{b}+\frac{\cos
C
}{c}\] \[=\frac{{{b}^{2}}+{{c}^{2}}-{{a}^{2}}+{{a}^{2}}+{{c}^{2}}-{{b}^{2}}+{{a}^{2}}+{{b}^{2}}-{{c}^{2}}}{
2ABC
}\] = \[\frac{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}}{2abc}\].