The diagonal of a hexagon is twice in length then it's opposite sides why? Give proof

Lets assume a hexagon ABCDEF. call the centre of the hexagon O. Now we know that angle AOB is 60 degree ( this is a property of hexagon). So triangle AOB is an equilateral triangle. Hence AO = side of the hexagon. Similarly DO= side of the triangle. Therefore, diagonal= AD= AO+OD = 2*side of triangle

Sorry in the above answer, I meant side of the hexagon in the last line. If you have any further doubts, feel free to ask