Question 1151147
<pre>
Draw a circle passing through A & B tangent to CD.   
Let 
 r be the radius 
 h the distance from the center O of the circle to the line AB
 M the midpoint of line AB

Then:
{{{ h = 10-r  }}}   (1)
and
{{{ h^2 + (4/2)^2 = r^2 }}}  (2)    (from the triangle OAM)


Substitute (1) into (2) to eliminate h:
{{{ (10-r)^2 + 4 = r^2 }}}

This simplifies to  r=5.2cm,  so the circle has an area of  approximately {{{highlight(85cm^2) }}}