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Analytical Geometry

Blazing goIITian

Joined:	31 Jan 2007
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7 Apr 2008 11:43:12 IST

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637

line eqn:!!!!!!!!!rates assured

None

how to convert a line's eqn from ax+by+c-0 form to x-x1/x2-x1 =y-y1/y2-y1 form

in Q like finding foot of perpendicular v need the 2nd form.

plz reply soon

urrrrrrrrrgenttttttttttttttttttt

rates assured

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Comments (7)

joy francis

Blazing goIITian

Joined: 19 Feb 2007

Posts: 1802

7 Apr 2008 11:56:19 IST

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Can u plz post the question..i don't think there is any compulsion on converting the line from this form to that form..

waise it is easy ..just take any 2 points satisfying the given line and then put the points in the eqn of two point form to get the eqn..

But i don't see any good in doing this..plz post the qn!

ashish banga

Blazing goIITian

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Posts: 1362

7 Apr 2008 12:01:07 IST

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slope of line = -a/b = tan theta
from tan theta given u can find cos theta and sin theta
this line also passes through a point which can be found by putting x= 0 we can get y coordinate when x =0
equation of line becomes
x - x1/ costheta = y -y1/ sin theta

varsha valli g.

Blazing goIITian

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7 Apr 2008 12:32:33 IST

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Q:find the foot of the perpendicular from the pt. (1,2)
to the line 3x+y+1=0.

!!!!!!!!!!

Rahul Raghavendra

Blazing goIITian

Joined: 9 Jan 2008

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7 Apr 2008 12:39:36 IST

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Let x-3y+ $\mu$ =0 be the line perpendicular to 3x+y+1=0 {mu is a constant}

Since it passes through (2,1)

It must surely satisfy it.

$2-3(1)+\mu=0\\\\ \mu=1$

Thus ans is

x-3y-1=0

Rahul Raghavendra

Blazing goIITian

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7 Apr 2008 12:40:15 IST

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solve the two eqn to get the final answer

seraphic

Hot goIITian

Joined: 1 Apr 2008

Posts: 124

7 Apr 2008 12:52:13 IST

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foot of perpendicual of a point (x₁, y₁) on the line ax+by+c=0 can b found using....

[ where (h,k) is the foot of perpendicular]

(h-x₁)/a = (k-y₁)/b = -[ax₁ +by₁ +c]/(a²+b²)

/-\|\|(|-|/-\|_

Scorching goIITian

Joined: 11 Mar 2007

Posts: 268

7 Apr 2008 13:30:27 IST

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see
d lyn perpendicular to line 3x+y+1=0 will hav slope -(1/3)
now we noe d equation of line passing thru point (1,2) nd having slope -(1/3)
solve this equation with 3x+y+1=0
nd find coordinate

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