The sum of all the interior angles of a decagon is
1440∘
A decagon is a polygon having 10 sides.
∵ The sum of interior angles of a polygon having 'n' sides is (n-2) × 180∘.
∴ sum of interior angles of a decagon= (10-2) × 180∘
= 8 × 180∘
= 1440∘