Area = ${1 \over 2}(5)(12)\sin \theta = 30$ $\sin \theta = 1 \Rightarrow \theta = {\pi \over 2}$ $\Delta$ is right angle $\Delta$ $r = (s - a)\tan {A \over 2}$ r = (s - a)$$$$\tan {{90} \over 2} $r = (s - a)$ $2R + r = s$, (As $a = 2R$) $2R + r = {{5 + 12 + 13} \over 2} = 15$