+129899 AE and BF are parallel
On AE locate D such that ED = 1
Then AD = BF
Connect FD
Then FD = AB
And triangle EDF is right with hypotenuse FD = 19 and legs ED = 1 and EF
So EF = sqrt ( 19^2 - 1^2) = sqrt (360) = 6sqrt 10
And CF = 1/2 EF = 3sqrt (10) = sqrt (90)
And triangle CFB is right with FC = sqrt 90 , BF = 9 and BC = the hypotenuse
So
BC = sqrt ( (sqrt 90)^2 + 9^2 ) = sqrt [ 90 + 81 ] = sqrt [ 171] ≈ 13.076
