The vertices of a quadrilateral in the coordinate plane are known. How can the perimeter of the figure be found? Use the distance formula to find the length of each side, and then add the lengths. Use the slope formula to find the slope of each of side, and then determine if the opposite sides are parallel. Use the slope formula to find the slope of each of side, and then determine if the consecutive sides are perpendicular. Use the distance formula to find the length of the sides, and then multiply two of the side lengths.