Three vectors →P, →Q, →R are such that the |→P|=|→Q|, |→R|=√2|→P| and →P+→Q+→R=0. The angle between →P and →Q, →Q and →R and →P and →R will be respectively.
A
90o,135o,135o
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B
90o,45o,45o
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C
45o,90o,90o
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D
45o,135o,135o
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Solution
The correct option is A90o,135o,135o
SQUARING P+Q+R=0 gives
P2+Q2+R2+2PQcosθ1+2QRcosθ2+2PRcosθ3=0.
Now putting the values of Q
and R in terms of P gives
cosθ1+20.5×(cosθ2+cosθ3)=−32.
Now putting values of
all angles from options we get