Question 454773
If we consider the regular decagon, its area is given by the formula:

{{{A=p*a/2}}}, where p is the perimeter and a the apotem ( Apotem is the line  

segment from the center of decagon perpendicular to the side)

{{{a=1/tan18=3.08}}}inches. and {{{A=20*3.08/2=30.8}}} square inches.