If $\cot x = \frac { 5 } { 12 }$ for some $\mathrm { x } \in \left( \pi , \frac { 3 \pi } { 2 } \right)$ then $\sin 7 x \left( \cos \frac { 13 x } { 2 } + \sin \frac { 13 x } { 2 } \right) + \cos 7 x \left( \cos \frac { 13 x } { 2 } - \sin \frac { 13 x } { 2 } \right)$ is equal to