Q. 15

Mark (√) against the correct answer in the following:

If and are mutually perpendicular unit vectors then

A. 3

B. 5

C. 6

D. 12

Answer :

Given are mutually perpendicular unit vectors


|


And angle between the vectors is and =0


Asking to find (3


Multiplying ,


=(35)- (36) ( + (25)(- (26)


= 15( [reason: dot product is commutative i.e,


=15-8(-12


=15-12 [reason:=0]


= 3

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