Question

prove that vector A=î+2jcap+3kcap and B=2î -jcap are perpendicular

Answer 1

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Answer 2

Use the dot product of vectors...

A.B = |A|.|B|.cos x
=> cos x = [ (A.B) / ( |A|.|B| ) ]
and it should be equal to 0
i.e, cos x = 0
=> cos x = cos 90°
=> x = 90°
So, the vectors are perpendicular .