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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता १२ वी

Reduce the equation rijkr¯.(3i^+4j^+12k^) to normal form and hence find (i) the length of the perpendicular from the origin to the plane (ii) direction cosines of the normal. - Mathematics and Statistics

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प्रश्न

Reduce the equation `bar"r".(3hat"i" + 4hat"j" + 12hat"k")` to normal form and hence find
(i) the length of the perpendicular from the origin to the plane
(ii) direction cosines of the normal.

बेरीज

उत्तर

The normal form of equation of a plane is `bar"r".hat"n" = p` where `hat"n"` is unit vector along the normal and p is the length of perpendicular drawn from origin to the plane.
Given pane is `bar"r".(3hat"i" + 4hat"j" + 12hat"k")` = 78       ...(1)
`bar"n" = 3hat"i" + 4hat"j" + 12hat"k"` is normal to the plane

∴ `|bar"n"| = sqrt(3^2 + 4^2 + 12^2) = sqrt(169)` = 13
Dividing both sides of (1) by 13,  get

`bar"r".((3hat"i" + 4hat"j" + 12hat"k")/13) = (78)/(13)`

i.e. `bar"r".(3/13hat"i" + 4/13hat"j" + 12/13hat"k")` = 6
This is the normal form of the equation of plane.
Comparing with `bar"r".hat"n" = p`,
(i) the length of the perpendicular from the origin to plane is 6.
(ii) direction cosines of the normal are `(3)/(13),(4)/(13),(12)/(13)`.

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पाठ 6: Line and Plane - Exercise 6.3 [पृष्ठ २१६]

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