Three Dimensional Geometry — MATHS STD 12 Science — Question
Rajasthan BoardEnglish MediumSTD 12 ScienceMATHSThree Dimensional Geometry3 Marks
Question
Write the plane $\vec{\text{r}}.(2\hat{\text{i}}+3\hat{\text{j}}-6\hat{\text{k}})=14$ in normal form.
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Answer
The given equation of the plane is
$\vec{\text{r}}.(2\hat{\text{i}}+3\hat{\text{j}}-6\hat{\text{k}})=14$ or $\vec{\text{r}}.\vec{\text{n}}=14$, where $\vec{\text{n}}=2\hat{\text{i}}+3\hat{\text{j}}-6\hat{\text{k}}$
$|\vec{\text{n}}|=\sqrt{4+9+36}=7$
For reducing the given equation to normal form, we need to divide it by $|\vec{\text{n}}|$.
Then, we get $\vec{\text{r}}.\frac{\vec{\text{n}}}{|\vec{\text{n}}|}=\frac{14}{|\vec{\text{n}}|}$
$=\vec{\text{r}}.\Big(\frac{2\hat{\text{i}}+3\hat{\text{j}}-6\hat{\text{k}}}{7}\Big)=\frac{14}{7}$
$\Rightarrow\vec{\text{r}}.\Big(\frac{2}{7}\hat{\text{i}}+\frac{3}{7}\hat{\text{j}}-\frac{6}{7}\hat{\text{k}}\Big)=2,$ which is the required normal form.
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