<Tr> <Th> Symmetry group </Th> <Td> Dihedral (D), order 2 × 8 </Td> </Tr> <Tr> <Th> Internal angle (degrees) </Th> <Td> 135 ° </Td> </Tr> <Tr> <Th> Dual polygon </Th> <Td> Self </Td> </Tr> <Tr> <Th> Properties </Th> <Td> Convex, cyclic, equilateral, isogonal, isotoxal </Td> </Tr>

How many diagonals are there in an eight sided regular polygon