Question 940995
<pre>
{{{drawing(500,600,-12,18,-18,18,line(-sqrt(84),0,sqrt(273),0),
line(0,-4,0,4),line(-sqrt(84),0,0,4), line(sqrt(273),0,0,4),
circle(-sqrt(84),0,10),circle(sqrt(273),0,17),
locate(-9.2,0,A), locate(0.2,0,B), locate(16.6,0,C), locate(0.3,4.8,D)

 )}}}

Sorry, I thought the common chord was 8 instead of 16.  You can 
change it for common chord of 16.

AD = 10 cm (radius)
BD = 4 cm (half of common chord which is 8 cm)
AB = {{{sqrt(10^2-4^2) =sqrt(100-16)=sqrt(84)=sqrt(4*21)=2sqrt(21)}}} cm

CD = 17 cm (radius)
BD = 4 cm (half of common chord which is 8 cm)
AC = {{{sqrt(17^2-4^2) =sqrt(289-16)=sqrt(273)}}}cm

AC = AB+BC = {{{2sqrt(21)+sqrt(273)}}}cm = about 25.69 cm.

Edwin</pre>