February 29th, 2012, 07:24 AM  #1 
Senior Member Joined: Sep 2011 From: New York, NY Posts: 333 Thanks: 0  Vectors Cross Product I am a little confused about the first one. I thought you would just take the coefficients of the x,y,z in both equations, and cross them. Knowing that the cross product of two vectors is a vector orthogonal to both vectors. eg: BUT the tutor at school told me that you have to take two vectors that satisfy the equations and cross those vectors. Eg: can some one please help me out with this? Separately, for the third question, I think to find the intersection of the two planes you just set the two equations equal to each other and solve. is that correct. or no because you have two equations and three variables??? Help with either would be appreciated! 
February 29th, 2012, 02:57 PM  #2 
Global Moderator Joined: May 2007 Posts: 6,276 Thanks: 516  Re: Vectors Cross Product
The normals are obtained as you described, but you need to adjust the lengths to be 1. The angle can be gotten quickly by observing that the dot product of the normals = 0, so the planes must be perpendicular. The cross product of the normals points along the line of intersection. To get the line you need to get one point on the line, so the line is given by this point plus a scalar parameter multiplying that cross product. I don't understand what the tutor was driving at. 

Tags 
cross, product, vectors 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Cross product between unit vectos  Jhenrique  Linear Algebra  0  January 14th, 2014 01:24 PM 
A question about cross product  Channeltsui  Linear Algebra  1  January 26th, 2013 06:10 PM 
A Question about Cross Product  Channeltsui  Linear Algebra  2  January 11th, 2013 10:21 AM 
Cross Product  aaronmath  Calculus  1  February 6th, 2012 02:44 PM 
cross product [a]x  dimevit  Linear Algebra  2  October 18th, 2007 03:45 AM 