Three Dimensional Geometry Question 238
Question: If direction ratios of two lines are $ 5,-12,,13 $ and $ -3,,4,,5 $ then the angle between them is
[RPET 2001]
Options:
A) $ {{\cos }^{-1}}(1/65) $
B) $ {{\cos }^{-1}}(2/65) $
C) $ {{\cos }^{-1}}(3/65) $
D) $ \pi /2 $
Show Answer
Answer:
Correct Answer: A
Solution:
$ \theta ={{\cos }^{-1}}\frac{(-15-48+65)}{\sqrt{25+144+169}\sqrt{9+16+25}} $ = $ {{\cos }^{-1}}( \frac{2}{(13\sqrt{2}),(5\sqrt{2})} ) $ = $ {{\cos }^{-1}}( \frac{1}{65} ) $ .
BETA
