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Analytical Geometry

akshay A NEW BEGINNING...'s Avatar
Blazing goIITian

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20 Mar 2009 13:56:29 IST
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hi...its urgently needed
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hi...its urgently needed


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akshay A NEW BEGINNING...'s Avatar

Blazing goIITian

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20 Mar 2009 13:58:36 IST
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soory here is the Q...

 

Find the distane of point ( -2,3,-4) form the line x+2 / 3 = 2y+3 / 4 = 3z-4 / 5   measured alone the plane 4x+12y -3z = 11 ???

vat kat's Avatar

Cool goIITian

Joined: 11 Mar 2009
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20 Mar 2009 14:24:48 IST
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confirm is it right because i a plane there r many directions and in which direction we have to find the length.question wud have been ok if we would have been given a line instead of planein abetter wy it is equivalent to asking find length of some line in the direction of x-y plane

Blazing goIITian

Joined: 21 Oct 2008
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20 Mar 2009 14:29:19 IST
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I will give u the hint...1.First find the distance from the line2. Find the angle between the line and the plane3. Use dot product of the D.RRate it if useful/.....

Hot goIITian

Joined: 21 Oct 2007
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20 Mar 2009 14:32:34 IST
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The fool-proof solution for this question is as follows-

1. Find the equation of the plane which is parallel to the given plane and passes through given point.

2. find the point where this plane cuts the given line.

3. Find the distance between the point obtained and the given point. this distance is the answer required.


Blazing goIITian

Joined: 21 Oct 2008
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20 Mar 2009 14:39:21 IST
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It is a tidious task Jayant... I hav faced a similar sum in my half-yearly..It takes lots of time coz usually the points that u get will be in fraction.. to square and to take square root will be a enormous job... Best way to do is to use dot product!!


Hot goIITian

Joined: 21 Oct 2007
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20 Mar 2009 14:42:33 IST
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I know that dot product is very convenient way to do it but it can confusing sometimes. If one has practised it well, then he can surely use the dot product.

akshay A NEW BEGINNING...'s Avatar

Blazing goIITian

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20 Mar 2009 15:03:50 IST
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ya i am too confused..because normally we have to find distance from plane parallel to line....but no here...
akshay A NEW BEGINNING...'s Avatar

Blazing goIITian

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20 Mar 2009 15:04:38 IST
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and @ jayant plsssss solve it .....fully...
akshay A NEW BEGINNING...'s Avatar

Blazing goIITian

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20 Mar 2009 15:08:50 IST
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@ sriraghav i am not getting ur method..
akshay A NEW BEGINNING...'s Avatar

Blazing goIITian

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20 Mar 2009 17:52:04 IST
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stills no answers.............
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Blazing goIITian

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20 Mar 2009 18:09:54 IST
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Q. Find the distane of point ( -2,3,-4) form the line x+2 / 3 = 2y+3 / 4 = 3z-4 / 5   measured along the plane 4x+12y -3z = 11  ??

 

well, here's my attempt :

im assuming dat u meant d divided by thing fr d whole thing in ur line eqn .....

(x + 2 ) / 3 = ( y + 3/2 )/ 2 = ( z - 4/3 ) / 5/3  = K

so let pt. on line be   A ( 3K - 2 ,  2K - 3/2 , 5K/3 + 4/3 )

and let B be ( -2, 3, -4 )

dr of AB = ( 3K, 2K - 9/2 , 5K/3 +16/3 )

now, u r given dat Ab is measured along d  plane 4x+12y -3z = 11  ....

so Ab is perpendicular 2 normal 2 plane

and normal has dr ( 4, 12, -3 )

so sum of product of drs = 0

and u get  3K*4  + 12*( 2K - 9/2)  + -3 * ( 5K/3 +16/3) = 0

find K

get d point

use distance formula ....

JOB DONE !!

 

 

 

Lakshmi's Avatar

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Joined: 4 Dec 2008
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20 Mar 2009 18:11:22 IST
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1) First find the pts on the line: x= 3K-2, y= 4k-3/2, z= 5k+4/32)then find the dr's of the line joining x.y,z and (-2, 3, -4)3)the normal to the plane and the line are perpendicular.4)find k5)get pt on line and find dist using dist fml



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