For a regular polygon, with 8 sides, me set side leng=2 & got
Area=19.313708
& outside serkel radius=2.6131259
yu want outside rad=7.4, so 7.4/2.6131259=2.831857432
so tri side leng=2*2.83...=5.663714863
get poly area=154.884673, rim-leng=45.3097189
polygon hite=13.673417
alfa=45 deg, beta=67.5, inside angel=135, outside=45 deg