Angle between two Vectors 2D

Question

I'm trying to compute the angle between two vectors. I tried this, but it always returns zero:

public double GetAngle(Vector2 a, Vector2 b)
{
    double angle = Math.Atan2(b.Y, b.X) - Math.Atan2(a.Y, a.X);
    return angle;
}

GetAngle(new Vector2(1,1), new Vector2(50,50));

Answer 1

You should take a look at the documentation of atan2 (here).

What you're looking of is finding the difference between B (your upper left vector) and A (your bottom right vector), then pass this as a parameter to atan2

return Math.Atan2(b.Y - a.Y, b.X - a.X);

What your code currently does is find the angle of the vector b in reference to 0,0 and subtract the angle of the vector a in reference to 0,0.

The reason you always get 0 is because 1,1 and 50,50 are on the same line that crosses 0,0 (both calls return something approx. 0.785398), so subtracting them will result in 0