Finding an angle with 3 CGPoints

Question

In my application, a user taps 3 times and an angle will be created by the 3 points that were tapped. It draws the angle perfectly. I am trying to calculate the angle at the

Answer 1

The way I have done it is to calculate the two angles separately using atan2(y,x) then using this function.

static inline double
AngleDiff(const double Angle1, const double Angle2)
{
    double diff = 0;
    diff = fabs(Angle1 - Angle2);
    if (diff > ) {
        diff = (<2Pi>) - diff;
    }
    return diff;
}

The function deals in radians, but you can change to 180 and <2Pi> to 360