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 2 Lines in a 3D field

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I want to prove that two lines that start from the same spot (O) and have the endpoints A=(-4,1,5) and B=(5,-4,4) have a 90 degree angle between each other. How do i go on about his?

 

If OA*OB= 0 the have a 90 degree angle right? My asnwer was 10 but I'm sceptical about all this

 Sep 17, 2015
edited by Guest  Sep 17, 2015

Best Answer 

 #1
avatar+130516 
+10

Two vectors are orthogonal[perpendicular] if their dot product = 0

 

I'm assuming that "O"  is the point (0, 0, 0).....if so,  we have

 

< -4, 1, 5 >  (dot) < 5, -4, 4  >   = -20 - 4 + 20  = -4  .....so......these vectors are not orthogonal

 

 

 

 

 

cool cool cool

 Sep 17, 2015

1+0 Answers

 #1
avatar+130516 
+10
Best Answer

Two vectors are orthogonal[perpendicular] if their dot product = 0

 

I'm assuming that "O"  is the point (0, 0, 0).....if so,  we have

 

< -4, 1, 5 >  (dot) < 5, -4, 4  >   = -20 - 4 + 20  = -4  .....so......these vectors are not orthogonal

 

 

 

 

 

cool cool cool

CPhill Sep 17, 2015

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