32.(2023•浦东新区模拟)已知OOO是ΔABC\Delta ABCΔABC的外心,且3OA→+4OB→+5OC→=0→3\overrightarrow{OA}+4\overrightarrow{OB}+5\overrightarrow{OC}=\overrightarrow 03OA+4OB+5OC=0,则cos∠BAC=\cos \angle BAC=cos∠BAC=___1010\frac{\sqrt{10}}{10}1010___.