Understanding cutting plane proofs I am trying to understand the following definition:
Def: A cutting plane proof from the system $Ax\leq b$ for an inequality $c^Tx\leq d$ is a sequence of inequalities $c_i^T\leq d_i$, $(i = 1,\ldots, k)$ with the following properties
i) every $c_i$ is integral,
ii) $c_k = c$ and $d_k = d$,
iii) for every $i$  there is a number $d_i'$ satisfying $\lfloor d_i'\rfloor \leq d_i$, such that $c_i^T x\leq d_i'$ is a nonnegative combination of the inequalities $Ax\leq b$ and $c_1^Tx\leq d_1,\ldots, c_{i-1}^Tx\leq d_{i-1}$.
Question: Could someone explain to me how the number $k$ is specified, and give an example of a cutting plane proof? I have tried to find examples that match this definition, but I haven't found any.
Thanks in advance!
 A: Suppose $Ax\le b$ is the following system:
$$(1): -x_1-3x_2\le -3\\
(2): 8x_1+3x_2\le 24\\
(3): -2x_1+x_2\le 1 $$
The solution set is represented by the following graph:

Suppose we want to derive $c^Tx\le b$ where $c^T=(0,1),b=3$, i.e., $x_2\le 3$ from $Ax\le b$.
From the picture, the problematic point is the intersection of (2) and (3). So we proceed as follows. First we obtain $c_1^Tx\le d_1$ by performing:
$$\frac{1}{2}\cdot((2)+(3)): 3x_1+2x_2\le 12.5.$$
Note that this is a nonnegative combination of the inequalities in $Ax\le b$. Now we set $d_1'=12$ which is the floor of $d_1=12.5$. This is $c_1^Tx\le d_1'$. We name it (4). Next we obtain $c_2^Tx\le d_2$ by performing:
$$\frac{1}{7}(3\cdot (3)+2\cdot(4)): x_2\le \frac{27}{7}.$$
Note that this is again a nonnegative combination of the inequalities in $Ax\le b$ and $c_1^Tx\le d_1'$. Making $d_2'=\lfloor d_2\rfloor=3$ gives the desired result. So $k=2$ and $c_2^Tx\le d_2'$ is exactly $c^Tx\le d$.
P.S. I think there are some typos in your definition. 
