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Given the coordinates of three 2-dimensional points $A$, $B$ and $C$, find the vectors $\\vec{AB}$, $\\vec{AC}$ and $\\vec{CB}$.

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The points A, B and C have coordinates $(\\var{a[0]},\\, \\var{a[1]})$, $(\\var{b[0]},\\, \\var{b[1]})$, and $(\\var{c[0]},\\, \\var{c[1]})$ respectively. 

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Find:

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To find the vector between two points, it can help to mark the points and their corresponding position vectors on a graph. In this case, let $\\bf a$, $\\bf b$ and $\\bf c$ be the position vectors of $A$, $B$, and $C$, such that 

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\\[ \\mathbf a = \\var{a}, \\quad \\mathbf b = \\var{b}, \\quad \\mathbf c = \\var{c}.\\]

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{geogebra_applet('https://www.geogebra.org/m/jrrcctdj',defs)}

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To find the vector $\\vec{AB}$, consider how you can get between $A$ and $B$ only 'travelling' along the position vectors. Firstly, we need to go from $A$ to the origin $O$, which is the vector $\\mathbf{-a}$, and then from the $O$ to $B$, which is the vector $\\mathbf b$. Therefore, $\\vec{AB} = \\mathbf{-a}+\\mathbf{b}$, or more simply, \\[ \\vec{AB} = \\mathbf {b} - \\mathbf{a}.\\] The same method applies for finding the vectors $\\vec{AC}$ and $\\vec{CB}$.

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Therefore,

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\\[ \\vec{AB} = \\mathbf{b}-\\mathbf{a} = \\var{sola}, \\]

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\\[ \\vec{AC} = \\mathbf{c}-\\mathbf{a} = \\var{solb}, \\]

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\\[ \\vec{CB} = \\mathbf{b}-\\mathbf{c} = \\var{solc}, \\]

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$\\vec{AB}$

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[[0]]

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$\\vec{AC}$

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$\\vec{CB}$

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