Question

Quantas Diagonais possui um octógono???

Answer 1

Octógono=8 lados

d=N*(N-3)/2
d=8*(8-3)/2
d=8*5/2
d=40/2
d=20
Resposta: 20 diagonais

Answer 2

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