x0=(x 1+x2)/2
y0=(y 1+y2)/2
You can draw a coordinate map if you have a reason. It can be explained by trapezoidal midline. Take the coordinates of A and B as vertical lines to form a trapezoid. The length of the midline is equal to the upper and lower base of the trapezoid, and then divided by 2.
The first senior high school physics teaching and research group work plan 202 1
Physics in senior high school