Answer:
A
Step-by-step explanation:
Find the distance of adjecent and opposite by forming new triangle that has (x1 and y1); (x2 and y2) distance... Using Pythagorean theorem, you can get the distance which is sqrt(x1²+y1²) and sqrt(x2²+y2²)
So you can use 1/2×base×height formula..
1/2×sqrt(x1²+y1²)×sqrt(x2²+y2²)
Simplify and you got A.
