which is known as a \emph{column vector}. Note that this notation assumes a specific choice of basis vectors, which is left
implicit, and displays only the information on its components along this specific basis.
For instance, if we had chosen the basis vectors $\textbf{\^i'}$ and $\textbf{\^j'}$, the components would be $x'$ and $y'$, and the corresponding column vector representing the same vector $\vec{r}$ in such case would be given by
For instance, if we had chosen another set of basis vectors $\hat{i}'$ and $\hat{j}'$, the components would be $x'$ and $y'$, and the corresponding column vector representing the same vector $\vec{r}$ in such case would be given by
$$
\vec{r}= \begin{pmatrix}x'\\y'\end{pmatrix}.
$$
...
...
@@ -162,11 +162,11 @@ where $r_1$ and $r_2$ indicate the *magnitude* (length) of the vectors
and $\theta$ indicates its relative angle. Note that the scalar product of two vectors is just a number, and thus
it must be *independent of the choice of basis*.
The same scalar product can also be expressed in terms of components of $\vec{r_1}$ and $\vec{r_2}$. When using the $\{\textbf{\^i},\textbf{\^j}\}$ basis, the scalar product will be given by
The same scalar product can also be expressed in terms of components of $\vec{r_1}$ and $\vec{r_2}$. When using the $\{\hat{i}, \hat{j}\}$ basis, the scalar product will be given by
@@ -183,5 +183,4 @@ where here we say that the vector $\vec{r_1}$ is represented by a *row vector*.
Therefore, we see that the scalar product of vectors in Euclidean space can be expressed as the matrix multiplication of row and column vectors. The same formalism, as we will see, can be applied for the case of Hilbert spaces in quantum mechanics.