How to get angle of point from center point?

Question

If I have 2 points (x0,y0) which is the center of the circle, and another point (x,y) (this is the red dot on the circle boundary in the image). How can I get the angle of the d

Answer 1

float AnglePointToPoint(const CCPoint & pFrom, const CCPoint & pTo)
{
    float distanceX     = pTo.x - pFrom.x;
    float distanceY     = pTo.y - pFrom.y;
    float beta          = acos( fabs(distanceX) / sqrt( pow(distanceX,2) + pow(distanceY,2) ) ) * 180 / M_PI;
    float angleResult   = 0.0f;

    if( distanceX > 0 )
    {
        if( distanceY < 0 )
        {
            angleResult = beta + 90;//right_bot
        }
        else
        {
            angleResult = fabs(beta - 90);//right_top
        }
    }
    else
    {
        if( distanceY < 0 )
        {
            angleResult = fabs(beta - 90) + 180;//left_bot
        }
        else
        {
            angleResult = beta + 270;//left_top
        }
    }
    return angleResult;
}