Question

30.
Let the angle between two nonzero vectors A
and B be 120° and resultant be Ċ :-
(1) C must be equal to A-B
(2) č must be less than Ä-B
(3) č must be greater than -B
(4) Č may be equal to A-B
Ans. 1​

Answer 1

Answer:

Here A,B,C are vectors 

|A+B|2 = |A|2 + |B|2+ 2A.B            (1) 

|A-B|2 = |A|2 + |B|2 - 2A.B             (2)

on subtracting (2) by (1)

|A+B|2 - |A-B|2 = 4A.B

so C2 = |A-B|2 + 4A.B

or C2 = |A-B|2 +4|A||B|cos120

since cos120 is negative so C will be less than |A-B|

Explanation:

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