Question

um decagono possui quantas diagonais

Answer 1

Formula:

d = n . (n - 3) / 2

Onde:
d = diagonais
n = número de lados

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Decágono  =  10 lados
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d = n . (n - 3) / 2
d = 10 . (10 - 3) / 2
d = 10 . 7 / 2
d = 70 / 2
d = 35

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O decágono possui 35 diagonais

Answer 2

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