Vector Algebra Question 299
Question: If the position vectors of A and B are $ \mathbf{i}+3\mathbf{j}-7\mathbf{k} $ and $ 5\mathbf{i}-2\mathbf{j}+4\mathbf{k}, $ then the direction cosine of $ \overrightarrow{AB} $ along y-axis is
[MNR 1989]
Options:
A) $ \frac{4}{\sqrt{162}} $
B) $ -\frac{5}{\sqrt{162}} $
C) 5
D) 11
Show Answer
Answer:
Correct Answer: B
Solution:
- $ \overrightarrow{AB}=4\mathbf{i}-5\mathbf{j}+11\mathbf{k} $ Direction cosine along $ y- $ axis $ =\frac{-5}{\sqrt{16+25+121}}=\frac{-5}{\sqrt{162}}. $
BETA
