Outer radius r_o
Outer radius r_o
Number of sides 7
Side length a_7=2*r_o*sin(pi/7)
Area $r_o*$r_o*7/2*sin(360/7)
sum of sides 7*a_7
Outer angle 360/7
Radius of inner circle r_i=a/(2*tan(36))
Diagonal d=sqrt((a_7/2)^2+(r_i+r_o)^2)
Height h = r_o  + r_i
Sum of angles 900


Description at Wikipedia

deesHeptagon (7 sides)
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