∴AB= 10,
Connect CP,
∵PD⊥AC at point D, PE⊥CB at point E,
∴ Quadrilateral DPEC is rectangular,
∴DE=CP,
When DE is minimum, CP is minimum. According to the shortest vertical line segment, CP is the smallest when CP⊥AB.
∴DE=CP=6×8 10=4.8,
So the answer is 4.8.