irregular octagon

The sum of the interior angles of a polygon is $(n-2)(180)$ where $n$ is the number of sides. So the sum of the interior angles of the figure is $(8-2)(180)=1080$ . We can use the principle of the area of a circular sector: the area of a circular sector is $\dfrac{\theta}{360} \pi r^2$ where $r$ is the radius of the circle. We have

$\color{#D61F06}\text{area of the red regions}=\dfrac{1080}{360}(3.14)(2^2)=\color{#69047E}\boxed{37.68~\text{square centimeters}}$

Area of the red regions is equivalent to 3 circle, so A=37.68.