How to determine the angle between two points?

Question

Geometry

There is such a task, you need to determine the angle between the points, the top point can move left and right
, you need a formula or something, how many x and y do we know

Answer 1

If there is a right angle between x and y - then these are the usual ratios in a right-angled triangle - so google it.
If not direct, then there is not enough data, if I remember correctly.

Answer 2

угол = arctg( y / x )
Would you like a little trigonometry ...