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

Possui 20 diagonais

Answer 2

$\large\displaystyle\boxed{\begin{array}{l} \rm{d = \dfrac{n \cdot(n - 3)}{2} \rightarrow \begin{cases} \rm \: d = diagonais \\ \rm \: n = n\acute{u}mero\,de\,lados \end{cases} } \\ \rm{d = \dfrac{8 \cdot(8 - 3)}{2} } \\ \\ \rm{d = \dfrac{8 \cdot5}{2} } \\ \\ \rm{d = \dfrac{40}{2} } \\ \\ \boxed{ \boxed{ \rm{d = 20}}} \checkmark\end{array}}$