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Commit 467a9a30 authored by Maciej Topyla's avatar Maciej Topyla
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fix admonitions

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1 merge request!161st major update src/3_vector_spaces.md
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...@@ -90,28 +90,26 @@ You might be already familiar with the concept of performing a number of various ...@@ -90,28 +90,26 @@ You might be already familiar with the concept of performing a number of various
!!! info "Scalar multiplication" !!! info "Scalar multiplication"
I can multiply a vector by a scalar number (either real or complex) to produce another vector, $$\vec{c} = \lambda \vec{a}$$. I can multiply a vector by a scalar number (either real or complex) to produce another vector, $$\vec{c} = \lambda \vec{a}$$.
Addition and scalar multiplication of vectors are both *associative* and *distributive*, so the following relations hold Addition and scalar multiplication of vectors are both *associative* and *distributive*, so the following relations hold
1. $(\lambda \mu) \vec{a} = \lambda (\mu \vec{a}) = \mu (\lambda \vec{a})$ 1. $(\lambda \mu) \vec{a} = \lambda (\mu \vec{a}) = \mu (\lambda \vec{a})$
2. $\lambda (\vec{a} + \vec{b}) = \lambda \vec{a} + \lambda \vec{b}$ 2. $\lambda (\vec{a} + \vec{b}) = \lambda \vec{a} + \lambda \vec{b}$
3. $(\lambda + \mu)\vec{a} = \lambda \vec{a} +\mu \vec{a}$ 3. $(\lambda + \mu)\vec{a} = \lambda \vec{a} +\mu \vec{a}$
- **Vector product**: in addition to multiplying a vector by a scalar, as mentioned above, one can also multiply two vectors among them. !!! info "Vector product"
There are two types of vector productions, one where the end result is a scalar (so just a number) and In addition to multiplying a vector by a scalar, as mentioned above, one can also multiply two vectors among them.
the other where the end result is another vectors. There are two types of vector productions, one where the end result is a scalar (so just a number) and the other where the end result is another vectors.
- The **scalar production of vectors** is given by $$ \vec{a}\cdot \vec{b} = a_1b_1 + a_2b_2 + \ldots + a_nb_n \, .$$ !!! info "The scalar production of vectors"
Note that since the scalar product is just a number, its value will not depend on the specific The **scalar production of vectors is given by $$ \vec{a}\cdot \vec{b} = a_1b_1 + a_2b_2 + \ldots + a_nb_n \, .$$
basis in which we express the vectors: the scalar product is said to be *basis-independent*. The scalar product is also found via Note that since the scalar product is just a number, its value will not depend on the specific
$$\vec{a} \cdot \vec{b} = |\vec{a}||\vec{b}| \cos \theta$$ basis in which we express the vectors: the scalar product is said to be *basis-independent*. The scalar product is also found via
with $\theta$ the angle between the vectors. $$\vec{a} \cdot \vec{b} = |\vec{a}||\vec{b}| \cos \theta$$ with $\theta$ the angle between the vectors.
- The **vector product** (or cross product) between two vectors $\vec{a}$ and $\vec{b}$ is given by !!! info "Cross product"
$$ "The vector product (or cross product) between two vectors $\vec{a}$ and $\vec{b}$ is given by
\vec{a}\times \vec{b} = |\vec{a}||\vec{b}|\sin\theta \hat{n} \, , $$ \vec{a}\times \vec{b} = |\vec{a}||\vec{b}|\sin\theta \hat{n}$$
$$ where $|\vec{a}|=\sqrt{ \vec{a}\cdot\vec{a} }$ (and likewise for $|\vec{b}|$) is the norm of the vector $\vec{a}$, $\theta$ is the angle between the two vectors, and $\hat{n}$ is a unit vector which is *perpendicular* to the plane that contains $\vec{a}$ and $\vec{b}$.
where $|\vec{a}|=\sqrt{ \vec{a}\cdot\vec{a} }$ (and likewise for $|\vec{b}|$) is the norm of the vector $\vec{a}$, $\theta$ is the angle Note that this cross-product can only be defined in *three-dimensional vector spaces*. The resulting vector
between the two vectors, and $\hat{n}$ is a unit vector which is *perpendicular* to the plane that contains $\vec{a}$ and $\vec{b}$. $\vec{c}=\vec{a}\times \vec{b} $ will have as components $c_1 = a_2b_3-a_3b_2$, $c_2= a_3b_1 - a_1b_3$, and $c_3= a_1b_2 - a_2b_1$.
Note that this cross-product can only be defined in *three-dimensional vector spaces*. The resulting vector $\vec{c}=\vec{a}\times \vec{b} $ will have as components $c_1 = a_2b_3-a_3b_2$, $c_2= a_3b_1 - a_1b_3$, and $c_3= a_1b_2 - a_2b_1$.
- A special vector is the **unit vector**, which has a norm of 1 *by definition*. A unit vector is often denoted with a hat, rather than an arrow ($\hat{i}$ instead of $\vec{i}$). To find the unit vector in the direction of an arbitrary vector $\vec{v}$, we divide by the norm: - A special vector is the **unit vector**, which has a norm of 1 *by definition*. A unit vector is often denoted with a hat, rather than an arrow ($\hat{i}$ instead of $\vec{i}$). To find the unit vector in the direction of an arbitrary vector $\vec{v}$, we divide by the norm:
$$\hat{v} = \frac{\vec{v}}{|\vec{v}|}$$ $$\hat{v} = \frac{\vec{v}}{|\vec{v}|}$$
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