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Question: Answered & Verified by Expert
If the foot of the perpendicular drawn from the origin to a plane is $M(-1,-2,2)$, then the vector equation of the plane is
MathematicsThree Dimensional GeometryMHT CETMHT CET 2022 (10 Aug Shift 1)
Options:
  • A $\bar{r} \cdot(-\hat{i}-2 \hat{j}+2 \widehat{k})=9$
  • B $\bar{r} \cdot(\widehat{i}+2 \widehat{j}+2 \widehat{k})=9$
  • C $\bar{r} \cdot(-\hat{i}-2 \hat{j}-2 \widehat{k})=9$
  • D $\bar{r} \cdot(\hat{i}+2 \hat{j}-2 \widehat{k})=9$
Solution:
2275 Upvotes Verified Answer
The correct answer is: $\bar{r} \cdot(-\hat{i}-2 \hat{j}+2 \widehat{k})=9$
D.r's of normal to the plane $<-1,-2,2>$
D.c's of Normal to the plane $<-\frac{1}{3},-\frac{2}{3}, \frac{2}{3}>$
length of perpendicular $=\sqrt{1^2+2^2+(-2)^2}=3$
Hence, Equation of plane $\vec{r} \cdot\left(-\frac{1}{3} \hat{i}-\frac{2}{3} \hat{j}+\frac{2}{3} \hat{k}\right)=3$
$\Rightarrow \vec{r} \cdot(-\hat{i}-2 \hat{j}+2 \widehat{k})=9$

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