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If cosalpha,cosbeta,cosgamma are the dir...

If `cosalpha,cosbeta,cosgamma` are the direction cosines of a vector `veca`, then `cos2alpha+cos2beta+cos2gamma` is equal to

A

3

B

0

C

2

D

`-1`

Text Solution

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The correct Answer is:
D
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TARGET PUBLICATION-THREE DIMENSIONAL GEOMETRY -Competitive Thinking
  1. If alpha,beta,gamma be the angles which a line makes with the coordina...

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  2. If cosalpha,cosbeta,cosgamma are the direction cosines of a vector vec...

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  3. If 1/2,1/3,n are direction cosines of a line, then the value of n is

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  4. If the direction cosines of a line are 1/c,1/c,1/c rthen (A) c.0 (B) 0...

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  5. A line AB in three-dimensional space makes angles 45^(@) and 120^(@) w...

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  6. If a line makes angle 120^(@) and 60^(@) with the positive directions ...

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  7. If a line makes an angle of pi/4 with the positive directions of ea...

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  8. If a vector barx makes angles with measure (pi)/(4) and (5pi)/(4) with...

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  9. A line makes 45^@ with positive x-axis and makes equal angles with pos...

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  10. If a line lies in the octant OXYZ and it makes equal angles with the a...

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  11. The number of lines which are equally inclined to the axes is :

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  12. If vector r wiith dc's l,m,n is equally inclined to the coordinate axe...

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  13. If a line makes angles alpha, beta and gamma with the coordinate axes,...

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  14. If a line makes angles (alpha)/(2), (beta)/(2), (gamma)/(2) with co-o...

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  15. The projection of a line segment on the co-ordinate 3, 4, 5, then its ...

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  16. The projection of a line segment on the coordinate axes are 2,3,6. The...

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  17. Find the direction of the joining the points P(4,3,-5) and Q(-2,1,-8)

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  18. A B C is a triangle and A=(235)dotB=(-1,3,2)a n dC=(lambda,5,mu)dot If...

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  19. If the direction ratios of a lines are proportional to 1,-3,2 then its...

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  20. Find the direction of the joining the points P(4,3,-5) and Q(-2,1,-8)

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