Question

quantas diagonais possui um octogono regular

Answer 1

Fórmula das diagonais : (n-3)n/2
d=(8-3)8/2
d=(5)(8)/2
d=40/2
d=20

Answer 2

$\large\boxed{\begin{array}{l} \rm \: d = \dfrac{n \: . \: (n - 3)}{2} \\ \\ \rm \: d = \dfrac{8 \: . \:(8 - 3) }{2} \\ \\ \rm \: d = \dfrac{8 \: . \: 5}{2} \\ \\ \rm \: d = \dfrac{40}{2} \\ \\ \boxed{ \boxed{ \rm{d = 20}}}\end{array}}$