Question

The resultant of vector A and vector B is vector R1 on reversing the vector B the resultant becomes R2 what is the value of R1 square + R2 square

Answer 1

according to formula 

R^2 = P^2 + Q^2 + 2PQ cosx 
and 
S^2 = P^2 + Q^2 - 2PQcosx 
add both 

R2+S2=2(P2+Q2) 
so independent of angle 
so d is answer