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NCERT Class XII Mathematics Chapter - - Solutions

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Question : 69 of 78
Marks: +1, -0
Find the coordinates of the point where the line through (5, 1, 6) and (3, 4, 1) crosses the YZ plane.
Solution:  
The equations of line through (5, 1, 6) and (3, 4, 1) are
x−53−5=y−14−1=z−61−6\frac{x-5}{3-5}=\frac{y-1}{4-1}=\frac{z-6}{1-6}
⇒x−5−2=y−13=z−6−5\Rightarrow\frac{x-5}{-2}=\frac{y-1}{3}=\frac{z-6}{-5}... (1)
Any point on (1) is (5 – 2k, 1 + 3k, 6 – 5k) ...(2)
This lies on YZ-plane
∴x=0\therefore x = 0
⇒5−2k=0⇒k=52\Rightarrow 5-2k=0 \Rightarrow k=\frac{5}{2}
Putting the value of k=52k=\frac{5}{2} in (2), (5−5,1+152,6−252)\left(5-5,1+\frac{15}{2},6-\frac{25}{2}\right)
i.e., (0,172,−132)\left(0,\frac{17}{2},-\frac{13}{2}\right) is the required point.
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