Question

If A=i+2j+3k and B = i+j+k then |A+B| is​

Answer 1

Answer:

Solution

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Correct option is D)

We have, a=i+2j+3k

∴b=i×(a×i)+j×(a×j)+k×(a×k) ...(i)

Now, i×(a×i)=(i.i)a−(i.a)i

=1(i+2j+3k)−(1)i

=2j+3k  

Similarly j(a×j)=i+3k

and k×(a×k)=i+2j

∴ From Eq. (i),

b=2j+3k+i+3k+i+2j

=2i+4j+6k

⇒∣b∣=  

4+16+36

​

=2  

14

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