Area of a triangle from coordinates

Steps

1. Draw the smallest rectangle around the triangle, with sides parallel to the axes.
2. Find the area of each right-angled triangle in the corners: ½ × run × rise, read from the coordinates.
3. Area of the triangle = rectangle − the corner triangles.

Worked examples

rectangle 6 × 5            = 30
corner triangles: ½·6·2 + ½·4·3 + ½·2·5 = 6 + 6 + 5 = 17
area = 30 − 17 = 13

For the whole topic, read Coordinates: key points, common mistakes and how the DSE tests it.

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