Question

o numero de diagonais de icosagono e: A)170 B)160 C)150 D)140 E)130

Answer 1

O icoságono tem 20 lados.

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

Alternativa a) 170

Answer 2

$\Large \text{ \sf{ d = \dfrac{n \cdot(n - 3)}{2} } }$

$\Large \text{ \sf{ d = \dfrac{20 \cdot(20 - 3)}{2} } }$

$\Large \text{ \sf{ d = \dfrac{20 \cdot17}{2} } }$

$\Large \text{ \sf{ d = \dfrac{340}{2} } }$

$\Large \text{ \boxed{ \boxed{\sf{ d = 170}}}\leftarrow\textsf{Letra A} }$