To find the perimeter of a polygon in the coordinate plane, you need to use the distance formula. This involves calculating the distance between each pair of adjacent vertices and summing these distances. The distance formula for two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is:
[tex]\[ \text{distance} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \][/tex]
So, the correct formula to use is the distance formula.
Therefore, the answer to the question is:
```
distance formula
```
