Question

um decágono regular possui quantas diagonais

Answer 1

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

Answer 2

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