Code Update and Typo - Githubissues

Hi @gaoxiang12 ,

First of all, thank you for your SLAM book repository, it's very useful to review the different parts of SLAM components with this book.

While reviewing the lectures, I found some typo with some of the chapters. Here are some of it:

In chapter 1, when talking about position in SLAM, the correct term for motion analysis is kinematics. Kinetics is the study of force on an object, whereas kinematic is the study of how motion works.
In chapter 2, in section 2.1.2, when specifying the determinant, there is repeated word of is, I've replaced it with "of" to avoid repetition.
In chapter 2, in section 2.2, there is a code error in explaining the basics of Eigen. In line 26, Vector3d v_3d and in line 28 Matrix<float, 3, 1> vd_3d, the comment specifies it is the same, in which it is not. I've fixed line 28 to Matrix<double, 3, 1> vd_3d. The comment specifying it is the same would then make sense. In doing so, to do the matrix multiplication of the Eigen in line 64 of the code, I then cast the variable vd_3d to a float to be able to do the calculation.

Do let me know your thoughts in this, and please give me any feedback on the changes.

gaoxiang12 / slambook-en