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Let veca , vecb , vecc be three unit vec...

Let `veca , vecb , vecc` be three unit vectors such that ` |veca + vecb +vecc| =1 and veca bot vecb , " if " vecc` makes angles ` delta beta " with " veca, vecb` respectively, then ` cos delta + cos beta ` is equal to

A

`3/2`

B

1

C

-1

D

`1/2`

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The correct Answer is:
C
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DISHA PUBLICATION-VECTOR ALGEBRA-EXERCISE -1 : CONCEPT BUILDER
  1. If veca , vecb ,vec c are the 3 vectors such that |veca| = 3, |vecb| ...

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  2. The vectors (2hati - mhatj+ 3mk) and {(1 + m) hati -2m hatj + hatk} i...

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  3. Let veca , vecb , vecc be three unit vectors such that |veca + vecb +...

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  4. If veca,vecb and vecc are three vectors of which every pair is non col...

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  5. The two vectors (x^2 - 1)hati +(x+2)hatj + x^2 hatk and 2hati -xhatj +...

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  6. The value of 'a' for which the points A, B,C with position vectors ...

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  7. For any vector veca the value of (vecaxxhati)^2+(vecaxxhatj)^2+(vecaxx...

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  8. If (veca xx vecb) xx vecc = vec a xx (vecb xx vecc), where veca, vecb ...

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  9. veca=3hati-5hatj and vecb=6hati+3hatj are two vectors and vec c is a v...

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  10. Vectors veca and vec b are inclined at an angle theta = 120^@ . If |ve...

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  11. For any vector vecp , the value of 3/2 { |vecp xx hati|^2 + |vecp ...

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  12. If (vec a xx vec b)^2 + (veca .vecb)^2 = 676 and |vecb| = 2, then |ve...

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  13. What is the interior acute angle of the parallelogram whose sides are ...

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  14. Area of rectangle having vertices A, B , C and D with position vector ...

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  15. Let veca,vecb and vecc be non-zero vectors such that no two are collin...

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  16. Let veca, vecb, vec c such that |veca| = 1 , |vecb| = 1 and |vec c | ...

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  17. |(a xx b).c | = |a||b||c| , if

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  18. If veca = hati +hatj , vecb = 2hatj - hatk " and " vecr xx veca = ve...

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  19. Let veca=hati-hatk, vecb=xhati+hatj+(1-x)hatk and vecc=yhati+xhatj+(1+...

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  20. If veca, vecb, vec c are three non coplanar vectors , then the value ...

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