Question

Calcule o número de diagonais de um: decágono

Answer 1

d=n(n-3)/2

d=10(10-3)/2

d=10x7/2

d=70/2

d=35

Answer 2

$\large\boxed{\begin{array}{l} \rm{d = \dfrac{n \cdot(n - 3)}{2}} \\ \\ \rm{d = \dfrac{10 \cdot(10 - 3)}{2} } \\ \\ \sf{d = \dfrac{10 \cdot7}{2} } \\ \\ \rm{d = \dfrac{70}{2} } \\ \\ \rm{d = 35} \end{array}}$