✔ 最佳答案
The East West distance between A and B = 20 cos50
The North South distance between A and B = 20 sin50
After moving a distance x to the north, the new North South distance between A and B = 20 cos50 - x
tan20 = (20 sin50 - x)/(20 cos50)
x = 20 sin50 - 20cos50 tan 20 = 10.64