"In a private project of mine, I have come across a challenging problem. I have 3 points: A, B and C. A is the motionless point of origin and C is the orbital point of destination. B is the linear transmission between the two; it must intersect with the changing position of C after leaving A, accounting for it's continued movement. The issue is, I'm not sure how to calculate whether or not B will meet C given certain values The equation attached to C should be familiar to most of you; it is the equation of a circle. (Cx-h)2+(Cy-k)2 = r2 At the core of my problem is that C is a point moving along this circle at a set rate (call the rate 't') B, however, is the problem point; B also moves, however it moves from A's a/b to C at a set rate ('s'). This gives us two extra variables: t = the rate of motion of C's orbit s = the rate of transmission of B There are some additional considerations to keep in mind. The line of transmission B moves on (B*) cannot be curved; it must remain linear. I need to figure out how to calculate the equation of this line from A to C given 's'. So far I have attempted treating the equation of a circle as one point in an equation for a line, however this gives me a range of lines, and from this point I don't know where to go. y= (xk+√(r2-(Cx-h)2)-b)/(h+√(r2-(Cy-k)2)-a)+b-(ka+√(r2a2-x2a2+2a2xh-h2)-ab)/(h+√(r2-(y-k)2)-a) But this would just give me the range of values given I know the current point of C. does anyone know how I can factor in the travel of C and the movement of B?