Take a little e from AB on the left, make AE=AD, and connect CE. The intersection c is CF perpendicular to EB, and the vertical foot is F.

Because AC is not good at splitting angles,

So angle DAC= angle EAC.

AC = AC again

So triangle EAC is equal to triangle EAC.

Therefore, CE=CD=CB= 10. EB=2 1-9= 12

Therefore, triangle CBC is an isosceles triangle.

In the right triangle ECD

CE= 10，EF=EB/2= 12/2=6

Applying Pythagorean Theorem, we get CF= 19.

So AF=AE+EF=9+6= 15.

In a right-angled triangle cafe,

AF= 15，CF=8

Applying Pythagorean Theorem, we get AC= 17.