Three Dimensional Geometry Question 158
If the co-ordinates of the points $ A,B,C $ be $ (-1,,3,,2),(2,,3,,5) $ and (3, 5,-2) respectively, then $ \angle A= $
Options:
A) $ 0{}^\circ $
B) $ 45{}^\circ $
C) $ 60{}^\circ $
D) $ 90{}^\circ $
Show Answer
Answer:
Correct Answer: D
Solution:
Equation of AB is $ \frac{x+1}{3}=\frac{y-3}{0}=\frac{z-2}{3} $ ?..(i) And that of AC is $ \frac{x+1}{4}=\frac{y-3}{2}=\frac{z-2}{-4} $ …..(ii) Hence $ \angle A={{\cos }^{-3}}( \frac{12+0-12}{\sqrt{9+9}\sqrt{16+4+16}} )=90^{o} $ .
BETA
