I basically have a circle with given radius and it's displacement from the origin and now I have to calculate the tangent to the circle at a given point. (Basically if I can get the slope of the tangent it's ok, I don't need more). I did use some google but I couldn't find an idea how to do this in Mathemathica? :/
So it is as easy as -(x1-x0)/(y1-y0) ?
is displacement from origin means the coordinates of the center (x0,y0) of the circle? If so, and you know a the coordinates of a given point on the circle say (x1,y1), then why is the radius also given? Not needed, you use use EuclideanDistance to find radius.
But if you know 2 points (x0,y0) and (x1,y1) already, then you can find the slope of this line (the radius). The tangent will be normal to this. So add 90 degrees?