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The dot product $\vec a\cdot\vec b$ of $\vec a = 2\hat i - \hat j + 3\hat k$ and $\vec b = \hat i + 4\hat j + 2\hat k$ is:
A$5$, missing a term in the dot product on the chart here
B$4$, since $2\cdot 1 + (-1)\cdot 4 + 3\cdot 2 = 2 - 4 + 6 = 4$
C$0$, claiming perpendicular vectors on the chart here
D$12$, summing all components without sign in the chart
Answer & Solution
Correct answer: B. $4$, since $2\cdot 1 + (-1)\cdot 4 + 3\cdot 2 = 2 - 4 + 6 = 4$
$\vec a\cdot\vec b = 2 - 4 + 6 = 4$.
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