get angle and radian between two points

Simple code for find angle between two points

The atan2 function is an extended version of the trigonometric inverse tangent function.
In the figure below, tan?=y/x, so tan-1y/x=?. The atan2 function just calculates tan-1y/x with y and x as separate parameters.
The reason it does so is to give a more accurate answer: since the tangent function is periodic,
there are multiple values of x and y that would appear to have the same angle (but do not).
Also, atan2 provides the correct values when y/x is undefined, such as at p/2.
%Input O-(x1,y1) and P-(x2,y2)points
%Output Angle
%devloper Er.Abbas Manthiri S
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