A unit vector is a vector that has length $\,1\,.$
When working with vectors $\,\langle a,b\rangle\,,$
two unit vectors
are singled out as being particularly important, and are given special names:
$$
\begin{gather}
\cssId{s4}{\hat{\smash{\imath}\vphantom{i}} = \langle 1,0\rangle}\cr
\cssId{s5}{\hat{\smash{\jmath}\vphantom{j}} = \langle 0,1\rangle}
\end{gather}
$$
The idea is as simple as ‘combining like terms’!
Just gather together the $\,\hat{\smash{\imath}\vphantom{i}}\,$ and $\,\hat{\smash{\jmath}\vphantom{j}}\,$ terms separately.
You don't always have $\,\hat{\smash{\imath}\vphantom{i}}\,$ first and
$\,\hat{\smash{\jmath}\vphantom{j}}\,$ second, so be careful.
They're often all mixed up.
Here's an example:
$$
\begin{align}
\cssId{s40}{3\hat{\smash{\jmath}\vphantom{j}} + 7\hat{\smash{\imath}\vphantom{i}} - 5(2\hat{\smash{\imath}\vphantom{i}} - \hat{\smash{\jmath}\vphantom{ij}})}
\quad &\cssId{s41}{=\quad 3\hat{\smash{\jmath}\vphantom{j}} + 7\hat{\smash{\imath}\vphantom{i}} - 10\hat{\smash{\imath}\vphantom{i}} + 5\hat{\smash{\jmath}\vphantom{ij}}}\cr\cr
\ &\cssId{s42}{=\quad -3\hat{\smash{\imath}\vphantom{i}} + 8\hat{\smash{\jmath}\vphantom{j}}}
\end{align}
$$
On this exercise, you will not key in your answer. However, you can check to see if your answer is correct. |
PROBLEM TYPES:
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