Three Dimensional Geometry Question 109
Question: If the direction cosines of a line are $ ( \frac{1}{c},\frac{1}{c},\frac{1}{c} ) $ , then
[JET 1989; CET 1993]
Options:
A) $ c>0 $
B) $ c=\pm \sqrt{3} $
C) $ 0 \lt c \lt 1 $
D) $c \gt 2$
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Answer:
Correct Answer: B
Solution:
Since direction cosines of line are $ ( \frac{1}{c},\frac{1}{c},\frac{1}{c} ) $
$ \therefore \frac{1}{c^{2}}+\frac{1}{c^{2}}+\frac{1}{c^{2}}=1\Rightarrow ,c^{2}=3,\Rightarrow c=\pm ,\sqrt{3} $ .
BETA
