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Vectors

Cool goIITian

Joined:	23 Jun 2011
Post:	65

28 May 2012 20:05:09 IST

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3D geometry

Engineering Entrance , JEE Main , JEE Advanced , Mathematics , Vectors

Find the angle between the lines whose direction cosines are given by the equations

3l+m+5n=0, 6mn-2nl+5lm=0

Comments (3)

P.SREEDHAR

Cool goIITian

Joined: 3 Oct 2011

Posts: 82

29 May 2012 17:55:50 IST

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cos^-1(1/6)

Benita

Cool goIITian

Joined: 23 Jun 2011

Posts: 65

29 May 2012 22:18:21 IST

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Could you tell me step wise hw u gt d ans?

P.SREEDHAR

Cool goIITian

Joined: 3 Oct 2011

Posts: 82

30 May 2012 10:53:22 IST

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take m=-5n-3l and substitute in second equation you will get a quadratic equation in terms of l and n . then u factorize it. take proportional values of m and n and find l then use cosA =L1L2+M1M2+N1N2

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