Question

R vector is resultant of P vector and Q vector if Q is reversed then resultant is S vector then proved that R sauare +S square = 2× P square + Q square

Answer 1

Hey there !!!!

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If P and Q are vectors then their resultant "R"= √(P²+Q²+2PQcos∅)

According to question when direction of Q is reversed 

Then resultant is "S"

So vectors are P and -Q

resultant(S)=√(P²+(-Q)²-2PQcos∅)

        S²=P²+Q²-2PQcos∅

       R²=P²+Q²+2PQcos∅

Adding these equations

 R²+S²=2(P²+Q²)

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Hope this helped you..................