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Analytical Geometry

Blazing goIITian

Joined:	24 Dec 2007
Post:	1111

20 Feb 2009 22:27:06 IST

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450

Line Question

Engineering Entrance , JEE Main , JEE Advanced , Mathematics , Analytical Geometry

A st line passes thru A(-2,-3) and cuts line x+3y=9 and x+y+1=0 at B and C respectively. Find equation of the line if AB.AC=20

How do U go about this one??

Comments (3)

Sagar Saxena

Blazing goIITian

Joined: 8 Oct 2008

Posts: 8064

20 Feb 2009 23:22:01 IST

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A st line passes thru A(-2,-3) and cuts line x+3y=9 and x+y+1=0 at B and C respectively. Find equation of the line if AB.AC=20

put the points in the given from

B = (-2+ r₁ cos ,-3 + r₁ sin )

C = (-2+ r₂ cos ,-3 + r₂ sin )

where ::

r₁ . r₂ = 20

from the above equation find the value of where is the slope of the line

guru vignesh

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Joined: 12 Nov 2008

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21 Feb 2009 06:00:52 IST

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the answer is Y-X+1=0

Rizwan M

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Joined: 13 Nov 2008

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18 Mar 2009 20:56:48 IST

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Try origin shift to A(-2,-3) then line passes throguh origin so y= mx form use origin shift on both line as well ;get the equation simplified in m as use AB.AC =20 get the equation ;shift it back after simplification;

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