Remove lines outside plotted circle

Hi people.

I am plotting a circle using the rectangle function and then I am plotting several lines in the same plot using the line function; the lines are within the circle but also extend out of it (of course). How can I keep only the part of the lines within the circle? Or maybe plot the lines initially with a method that somehow confines them within the circle.

I am sure this is easily done as an image analysis problem, but I was wondering if it can be done with plots.

Thanks.