(a)[4]
Find the cosine of angle $BAC$ by using a scalar product.
(b)[4]
Hence determine the area of triangle $ABC$. Present your answer in simplified exact form.
Mathematics 9709 · AS & A Level · Vectors
Vectors — practice question
Measured from the origin $O$, the position vectors of $A$, $B$ and $C$ are $\vec{OA} = \begin{pmatrix} 1 \\ 3 \\ 1 \end{pmatrix}$, $\vec{OB} = \begin{pmatrix} 3 \\ 1 \\ 2 \end{pmatrix}$ and $\vec{OC} = \begin{pmatrix} 5 \\ 3 \\ -2 \end{pmatrix}$.
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