
This drawing shows the ideal line through a simple, 180 degree corner. The ideal line is drawn in
red, and the track edges in black. This type of driving line is called
Out-In-Out: approaching the corner, you take the outside, as far as possible, you take the inside line in the middle of the corner, and you take the outside again on the exit. The middle part of the corner, drawn in
blue, is called the apex of the turn, or the clipping point. The wider you can make the radius of the line, the faster you can take the corner. Or in other words, the less speed you'll lose.
Note that all the braking should be done in the straight line, before the circular part begins. The acceleration too begins after the circular part, when the car is tracking straight. During the circular part, the car's velocity is constant. It has to be, assuming that the radius of the path is constant and the tires are delivering maximum grip.
Click here for another illustration on 90 degrees out-in-out method.