Question

o numero de diagonais de um octonogo

Answer 1

Sendo d=diagonais e n=n° de lados

Um octógono tem 8 lados.

$d= \dfrac{n\times(n-3)}{2} \to \\\\\\d= \dfrac{8\times(8-3)}{2} \to \\\\\\d= \dfrac{8\times5}{2} \to \\\\\\d= \dfrac{40}{2} \to \\\\\\ \boxed{d=20}$