Vectors 2 Question 10

10. If the vectors a,b and c from the sides BC,CA and AB respectively of a ABC, then

(2000, 2M)

(a) ab+bc+ca=0

(b) a×b=b×c=c×a

(c) ab=bc=ca

(d) a×b+b×c+c×a=0

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Answer:

Correct Answer: 10. (a)

Solution:

  1. By triangle law, a+b+c=0

Taking cross product by a,b,c respectively,

a×(a+b+c)=a×0=0a×a+a×b+a×c=aa×b=c×a[a×a=0] Similarly, a×b=b×aa×b=b×c=c×a



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