Let n be the number of edges of the polygon \(\left(n\in N;n>2\right)\)

We have : \(180\left(n-2\right)=1260\Leftrightarrow n-2=7\Leftrightarrow n=9\)

So, the polygon has 9 sides.

Let n be the of edges of the polygon and (n ∈ N, n > 2)

We have :

180 . (n - 2) = 1260 <=> n - 2 = 7 => n = 9

Answer: 9 sides

Let n be the of edges of the polygon and (n ∈ N, n > 2)

We have :

180 . (n - 2) = 1260 <=> n - 2 = 7 => n = 9

Answer: 9 sides
 

( n ∈ N , n > 2 )(n∈N;n>2)

180 ( n - 2 ) = 1260 ⇔ n - 2 = 7 ⇔ n = 9180(n−2)=1260⇔n−2=7⇔n=9

Vì vậy, đa giác có 9 mặt.