Vector Algebra Question 356
Question: The value of x for which the angle between the vectors $ \mathbf{a}=x\mathbf{i}-3\mathbf{j}-\mathbf{k},\mathbf{b}=2x\mathbf{i}+x\mathbf{j}-\mathbf{k} $ is acute and the angle between the vectors b and the axis of ordinate is obtuse, are
Options:
A) 1, 2
B) ? 2, ? 3
C) x > 0
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
- According to the given conditions, $ \mathbf{a},.,\mathbf{b}>0 $ and $ \mathbf{b},.,\mathbf{c}<0, $ where $ \mathbf{c}=(0,1,0). $
$ \Rightarrow 2x^{2}-3x+1>0 $ and $ x<0. $ Hence the result.
BETA
