At △ABF, ∠ ABF = 90.
∴BF=6,
∴FC= 10-6=4,
Let EC=x, then ef = de = 8-X.
∫∠C = 90,
∴EC2+FC2=EF2,
∴x2+42=(8-x)2,
Solution: x=3,
∴EC=3(cm).