Typo in 7.2 "State-Space Representation of Dynamic Systems"

[iassenev]

1. "Convention allows us to write x(tk) as xk, which means the the value of x at the kth value of t." "Convention allows us to write x(tk) as xk, which means the value of x at the kth value of t."

2. "Once in this form we use of of several techniques to convert these linear differential equations into the recursive equation:" "Once in this form we use of several techniques to convert these linear differential equations into the recursive equation:"

3. "Many use instead of F." - missed a symbol, which is used instead of F.

4. "Finding this matrix is often quite difficult." Then there are 2 integrals, the first has a range [x_k-1, x_k], but then x_0 has been used instead of x_k-1

[MuhammedM294]

Except for the first point, all of them are already correct in the repo (master branch).