If P + Q = R and P - Q = S, prove that `R^2 + S^2 = 2(P^2 + Q^2)`

1.	If P + Q = R and P - Q = S, prove that `R^2 + S^2 = 2(P^2 + Q^2)`
Answer» `R^2 = P^2 Q^2 + 2PQ cos theta …..(i)` `S^2 = P^2 + Q^2 - 2PQ cos theta (i)` Adding these two equations we get, `R^2 + S^2 = 2(P^2 +Q^2)`

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If P + Q = R and P - Q = S, prove that `R^2 + S^2 = 2(P^2 + Q^2)`

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