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Assertion : If in a /\ABC, vec(BC)=vecp/...

Assertion : `If in a `/_\ABC, vec(BC)=vecp/|vecp|-vecq/|vecq| and vec(AC)=(2vecp)/|vecp|,|vecp|!=|veq|` then the value of `cos2A+cos2B+cos2C ` is -1., Reason: If in `/_\ABC, /_C=90^0 then cos2A+cos2B+cos2C=-1` (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true R is not te correct explanation of A (C) A is true but R is false. (D) A is false but R is true.

A

Both statement I and statement II are correct and statement II is the correct explanation of statement I

B

both statement I and statement II are correct but statement II is not the correct explanation of statement I

C

Statement I is correct but statement II is incorrect

D

Statement II is correct but statement I is incorrect

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The correct Answer is:
B
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ARIHANT MATHS-PRODUCT OF VECTORS-Exercise (Questions Asked In Previous 13 Years Exam)
  1. Assertion : If in a /\ABC, vec(BC)=vecp/|vecp|-vecq/|vecq| and vec(AC)...

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  2. Let O be the origin and let PQR be an arbitrary triangle. The point S ...

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  3. Let O be the origin and OX, OY, OZ be three unit vectors in the direct...

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  4. Let O be the origin, and O X , O Y , O Z be three unit vectors ...

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  5. Let a, b and c be three unit vectors such that atimes(btimesc)=(sqrt(3...

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  6. Let vec(a) , vec(b) and vec(c) be three non-zero vectors such that no ...

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  7. If a, b and c are unit vectors satisfying |a-b|^(2)+|b-c|^(2)+|c-a|^(2...

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  8. The vector(s) which is/are coplanar with vectors hat(i)+hat(j)+2hat(k)...

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  9. Let vec a =hat i+hat j+hat k,vec b=hat i -hat j+hat k and vec c =hat ...

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  10. Two adjacent sides of a parallelogram ABCD are given by vec(AB)=2hati+...

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  11. Let P, Q, R and S be the points on the plane with position vectors -2h...

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  12. If a and b are vectors in space given by a=(hat(i)-2hat(j))/(sqrt(5)) ...

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  13. If veca,vecb,vecc and vecd are unit vectors such that (vecaxxvecb)*(...

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  14. The edges of a parallelopiped are of unit length and are parallel to ...

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  15. Lelt two non collinear unit vectors hata and hatb form and acute angle...

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  16. Let the vectors PQ, QR, RS, ST, TU and UP represent the sides of a reg...

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  17. The number of distinct real values of lambda, for which the vectors -l...

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  18. Let veca,vecb,vecc be unit vectors such that veca+vecb+vecc=vec0. Whic...

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  19. Let A be vector parallel to line of intersection of planes P1 and P2. ...

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  20. Let a=hat(i)+2hat(j)+hat(k), b=hat(i)-hat(j)+hat(k), c=hat(i)+hat(j)-h...

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  21. If vec a , vec b and vec c are three non-zero, non coplanar vecto...

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