Vector Algebra Question 364
Question: The angle between the vectors $ (2\mathbf{i}+6\mathbf{j}+3\mathbf{k}) $ and $ (12\mathbf{i}-4\mathbf{j}+3\mathbf{k}) $ is
[MP PET 1996]
Options:
A) $ {{\cos }^{-1}}( \frac{1}{10} ) $
B) $ {{\cos }^{-1}}( \frac{9}{11} ) $
C) $ {{\cos }^{-1}}( \frac{9}{91} ) $
D) $ {{\cos }^{-1}}( \frac{1}{9} ) $
Show Answer
Answer:
Correct Answer: C
Solution:
- $ \theta ={{\cos }^{-1}}( \frac{2\times 12+6\times (-4)+3(3)}{\sqrt{2^{2}+6^{2}+3^{2}}\sqrt{12^{2}+4^{2}+3^{2}}} ) $ $ ={{\cos }^{-1}}( \frac{9}{7\times 13} )={{\cos }^{-1}}( \frac{9}{91} ) $
BETA
