Given three vertices of parallelogram ABCD:
A(3, 2)
B(1, -1)
C(2, 1)
The area of a parallelogram can be found using any three consecutive vertices by calculating the cross product of two adjacent sides.
Vector AB represents the side from A to B:
Vector AB = B - A
Vector AB = (1 - 3, -1 - 2)
Vector AB = (-2, -3)
Vector AC represents the side from A to C:
Vector AC = C - A
Vector AC = (2 - 3, 1 - 2)
Vector AC = (-1, -1)
For a parallelogram with adjacent sides represented by vectors (x₁, y₁) and (x₂, y₂):
Area = ∣x1×y2−x2×y1∣
Substituting AB = (-2, -3) and AC = (-1, -1):
Area = ∣(−2)×(−1)−(−1)×(−3)∣
Area = ∣2−3∣
Area = ∣−1∣
Area = 1
Therefore, the area of parallelogram ABCD is 1 square unit.