Question

1) Calcule o número de diagonais dos seguintes polígonos: a) eneágono b) decágono c) undecágono d) icoságono ​

Answer 1

Resposta:

A

$d = \frac{n(n - 3)}{2} \\ d = \frac{9(9 - 3)}{2} \\ d = \frac{9 \times 6}{2} \\ d = \frac{54}{2} \\ d = 27$

B

$d = \frac{10(10 - 3)}{2} \\ d = \frac{10 \times 7}{2} \\ d = \frac{70}{2} \\ d = 35$

C

$d = \frac{11(11- 3)}{2} \\ d = \frac{11 \times 8}{2} \\ d = \frac{88}{2} \\ d = 44$

D

$d = \frac{20(20 - 3)}{2} \\ d = \frac{20 \times 17}{2} \\ d = \frac{340}{2} \\ d = 170$