[填空题]
A land surveyor is measuring the area of a triangular plot of land on a smh he6k;p0z+d koottvw 3w+ )zgvcw2hn ;t/h hill. She uses a theodolite to determine the coor)gtc+ hw/zn2 ww;t3 vvdinates of the corners of the land and 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. $m^2$
