We're doing a bit about circles in Pure Maths at the mo and everything's fine about intersections etc until today the lecturer rammed up an easier eqt to tell if a line cuts a circle at 2 distint points or not. We had to show that the line 3y=x+5 cut the circle x^2 + y^2 -6x - 2y -15 in 2 distinct places. From before we found out that the centre of the circle was at (3,1) and the radius was five. It was then said tha the line would cut the circle in 2 distint places if its distance from the centre was less tha five. All that was fine until it was put up that this distance was the modulud of (-3 +3 -5)/(sqrt(3^2 + 1^2) whivh was clearly less than 5 so it cut it in 2 distinct places. How was this distance worked out? I asked some of the other people in the lecture about it and they were as confused as me. I mean it's obviously not rocket scientist stuff since the lecturer didn't even feel the need to tell us what was going on, so can someone please help? Thanks! Also, what forum should I post in if I want to ask about solving a heat transfer problem using he Fourier series? It's just about the general formula. Anyone here know much about it?