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if e2= (1,1,1) and e2=(1,1,-1) a and b are two vectors such that e1=2a+b and e2=a+2b then the angle between a and b is cos -1 (7/9) cos -1 (7/11) cos -1 (-7/11) cos -1 [6∫2/11]

if e2= (1,1,1) and e2=(1,1,-1) a and b are two vectors such that e1=2a+b and e2=a+2b then the angle between a and b is
  1. cos-1(7/9)
  2. cos-1(7/11)
  3. cos-1(-7/11)
  4.  cos-1[6∫2/11]

Grade:12th pass

1 Answers

ng29
1698 Points
7 years ago
on solving the equations between e1,e2,a and b 
we get  a= (1/3,1/3,1)
          b= (1/3,1/3,-1)
using  a.b=ab cosx         x  is the angle between a and b 
so answer is c)   cos-1(-7/11)
approve if useful

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