Because the intersection AC of the middle vertical line of the line segment CB is at point D, it can be known that BD=CD.

4-x=x- 1 solution: x=5/2.

AD=5/2，CD=3/2，BD=3/2

According to: COSA = (AB 2+AD 2-BD 2)/(2abad) = 0.8.

BC^2=AB^2+AC^2-2ABACcosA=36/5

BC=6/√5

Cos angle ACB = (AC 2+BC 2-AB 2)/(2 ABCC) = 2/√ 5.

I hope I can help you, thank you!