Three Dimensional Geometry Question 150
Question: If projection of any line on co-ordinate axis 3, 4, and 5, then its length is
[Pb. CET 2000]
Options:
A) 12
B) 50
C) $ 5\sqrt{2} $
D) $ 3\sqrt{2} $
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Answer:
Correct Answer: C
Solution:
Let d be the length of line, then projection on x-axis = $ dl=3 $ , projection on y-axis = $ dm=4 $ and projection on z-axis = $ dn=5 $ . Now, $ d^{2}(l^{2}+m^{2}+n^{2})=50\Rightarrow d^{2}(1)=50\Rightarrow d=5\sqrt{2} $ .
BETA
