Calculating angle a segment forms with a ray

Posted by kr1zz on Game Development See other posts from Game Development or by kr1zz
Published on 2014-08-20T15:30:15Z Indexed on 2014/08/20 16:37 UTC
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geometry

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angles

I am given a point C and a ray r starting there. I know the coordinates (xc, yc) of the point C and the angle theta the ray r forms with the horizontal, theta in (-pi, pi]. I am also given another point P of which I know the coordinates (xp, yp): how do I calculate the angle alpha that the segment CP forms with the ray r, alpha in (-pi, pi]?

Some examples follow: example 1 example 2 example 3

I can use the the atan2 function.

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