need a help with 3d geometry

th3_r34p3r · December 15th, 2012, 09:02 PM

Find direction cosines of line perpendicular to lines with direction cosines proportional to (6,4,-4) and (-6,2,1).

skipjack · December 16th, 2012, 06:13 AM

Find a vector, such as (2, 3, 6), that is perpendicular to (6, 4, -4) and (-6, 2, 1), then calculate ?(2� + 3� + 6�) = 7. Dividing (2, 3, 6) by 7 gives (2/7, 3/7, 6/7).

mathman · December 16th, 2012, 03:00 PM

Quote:

Originally Posted by th3_r34p3r

Find direction cosines of line perpendicular to lines with direction cosines proportional to (6,4,-4) and (-6,2,1).

To get a vector perpendicular to two vectors, take the cross product of the two vectors.

December 15th, 2012, 09:02 PM	#1
th3_r34p3r Newbie Joined: Dec 2012 Posts: 1 Thanks: 0	need a help with 3d geometry Find direction cosines of line perpendicular to lines with direction cosines proportional to (6,4,-4) and (-6,2,1).
$th3_r34p3r is offline$

December 16th, 2012, 06:13 AM	#2
skipjack Global Moderator Joined: Dec 2006 Posts: 20,281 Thanks: 1965	Find a vector, such as (2, 3, 6), that is perpendicular to (6, 4, -4) and (-6, 2, 1), then calculate ?(2� + 3� + 6�) = 7. Dividing (2, 3, 6) by 7 gives (2/7, 3/7, 6/7).
$skipjack is offline$

Thread Tools
$Show Printable Version$ Show Printable Version $Email this Page$ Email this Page
Display Modes
$Linear Mode$ Linear Mode $Hybrid Mode$ Switch to Hybrid Mode $Threaded Mode$ Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Geometry help!	PlzzHelp	Geometry	5	March 15th, 2014 10:47 PM
Coxeter's �Geometry Revisited� vs. �Introduction to Geometry	becko	Math Books	2	December 29th, 2010 09:47 PM
geometry 1 help	tobymac	Geometry	1	July 29th, 2009 03:48 PM
geometry	baxx45	Geometry	1	January 12th, 2009 10:19 AM
Use of plane geometry in coordinate geometry problems	cursed_mask	Geometry	0	July 23rd, 2008 12:52 AM