List the vertices in one continuous trip around the boundary and repeat the first point at the end. Form the two diagonal-product sums, take the absolute difference so orientation cannot make area negative, and divide by two; a quick sketch confirms the order before the arithmetic begins.
Inside Gozunta
Turn the preview into practice.
More than a preview
Gozunta lets you study this problem—and more than 10,000 others.
Create targeted learning sessions, use hints, check your answer, read the walkthrough, watch the video, print the work, and track your progress.