I need to calculate (previously) the point where a ball will touch the inside of a circle (for a game I'm developing). So I have two equations, one of the direction of the ball, and another of the circle (with variables related screen resolution of my game):
$$(x - W)^2 + (Y - H)^2 = r^2$$
$$Y = T(X - X_p) + Y_p$$
where: W = Screen weight / 2
H = Screen height / 2
Xp and Yp = Position of the ball
T = tangent of Direction D
I also did the equations this site: https://www.desmos.com/calculator/uupif7b2j9
I tried to calculate the system of equations, reaching an equation of 2nd degree, but when I resolve, not the result I expected.
sorry for my English
I am not sure if I understood correctly: line goes through center of a circle and you need intersection points of line and circle?
On your picture it looks like that. But line equation doesn't confirm this.