2017 AIME II Problems/Problem 10
Rectangle has side lengths and . Point is the midpoint of , point is the trisection point of closer to , and point is the intersection of and . Point lies on the quadrilateral , and bisects the area of . Find the area of .
Impose a coordinate system on the diagram where point is the origin. Therefore , , , and . Because is a midpoint and is a trisection point, and . The equation for line is and the equation for line is , so their intersection, point , is . Using the shoelace formula on quadrilateral , or or drawing diagonal and using , we find that its area is . Therefore the area of triangle is and the distance from to line is and its -coordinate is . Because lies on the equation , 's -coordinate is , which is also the height of . Therefore the area of is .
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