Q20 of 29 Page 1

If are three vectors such that, then prove that and hence show that

Given that


Take cross product with ,




As




We know that



Now take cross product of b with given




As




From (i) and (ii)



Hence proved


We also need to show that


Now means vector triple product which is


But



Now is perpendicular to .


As cos 90° = 1


So, the dot product of with a perpendicular vector to is 0.



Hence proved


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