Three-Dimensional-Geometry Question 417
Question: If the direction ratios of a line are $ 1,-3,,2 $ , then the direction cosines of the line are
[MP PET 1997, Pb. CET 2002]
Options:
A) $ \frac{1}{\sqrt{14}},\frac{-3}{\sqrt{14}},\frac{2}{\sqrt{14}} $
B) $ \frac{1}{\sqrt{14}},\frac{2}{\sqrt{14}},\frac{3}{\sqrt{14}} $
C) $ \frac{-1}{\sqrt{14}},\frac{3}{\sqrt{14}},\frac{-2}{\sqrt{14}} $
D) $ \frac{-1}{\sqrt{14}},\frac{-2}{\sqrt{14}},\frac{-3}{\sqrt{14}} $
Show Answer
Answer:
Correct Answer: A
Solution:
For D’ratio (1, ? 3, 2), the direction cosine will be $ ( \frac{1}{\sqrt{1+9+4}},,\frac{-3}{\sqrt{1+9+4}},,\frac{2}{\sqrt{1+9+4}} ) $
$ \Rightarrow ( \frac{1}{\sqrt{14}},,\frac{-3}{\sqrt{14}},,\frac{2}{\sqrt{14}} ) $ .
BETA
