Answer:
![A=50(1+\sqrt 2) \ cm^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/wkszp7sx66e14qk219xt19du3rkn72yngx.png)
Explanation:
We have given that the side length of a regular octagon is 5 cm. It is required to find the area of this octagon.
The formula used to find the area of a regular octagon is :
![A=2(1+\sqrt 2) a^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/ivo70ja2vjgt90atn7q3bbvgmjzl3103qi.png)
a is side length
So,
![A=2(1+\sqrt 2) * (5)^2\\\\A=2(1+\sqrt 2) * 25\\\\A=50(1+\sqrt 2) \ cm^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/4j7hcslv17lzdeodc6f5dk9tq3i2li7z9y.png)
So, the area of a regular octagon is
.