Ok I have been trying to figure this out myself but been stumbling over it too long and wanted some real math people to help me here.
I have the X,Y of my initial Touch, with my touch I pull back in any direction (think like Angry birds) which I then have the angle of my initial touch and my current touching point.
What I need is to be able to get the X,Y of a point the opposite angle I am pulling but only a certain amount of pixels. So essentially, where I am pulling back there should be a dot on the opposite side of the circle but only 30 px from the center point (not the distance of my current touch to the center, just a set amount). So I can just drag around and there should be a dot making a perfect circle at the same distance away from the center point.
Does that make sense?
I had been trying to set the dot using a formula I saw on here but it's not working on most angles.
X = X + 30 * cos(angle)
Y= Y + 30 * cos(angle)
Any help would be fantastic!