[填空题]
A land surveyor is measuring the area of a triangula* p5ho)p*r ontw9h4v cr plot of land onu eck89, y6stt a smooth hill. She uses a theodolite to determine the coordinates of the corners of the land and,ck98ys 6uett finds them to be (-8,20,10),(16,8,7) and (-20,-8,3) , where the coordinates are in metres from a fixed origin where she stands.
Using vectors, determine the area of the land. $m^2$
