The general formula to know how much is the sum of the interior agles of a polygon is:
![(n-2)\cdot180º](https://img.qammunity.org/2023/formulas/mathematics/college/2eizaibmydw7rzhl5oahp0uxtsasvw0jw4.png)
Where n is the number of sides.
Then:
In a polygon with 3 sides the internal angles sum: 180º
![(3-2)\cdot180º=180º](https://img.qammunity.org/2023/formulas/mathematics/college/eg6lt9cfo5kq1f9okma8s4coqvzw08xj0j.png)
In a polygon with 4 sides the internal angles sum: 360º
![(4-2)\cdot180º=360º](https://img.qammunity.org/2023/formulas/mathematics/college/b70j6lns5xidq88obs27x57b5u9xaxcz9j.png)
In a polygon with 5 sides the internal angles sum: 540º
![(5-2)\cdot180º=540º](https://img.qammunity.org/2023/formulas/mathematics/college/janu4u1vllazbuuz3sunkwi2xwm9ygmbck.png)