Draw a rough sketch of a regular octagon. (Use squared paper if you wish).
Draw a rectangle by joining exactly four of the vertices of the octagon.
Plot a diagram of a regular octagon and then join exactly four of the vertices of the octagon to form a rectangle.
Draw the diagram of a regular octagon and then join .
The diagram is shown below:
From the figure, observe that by joining , forms a rectangle.
Hence, the required diagram is shown below: