1.

The angles between P+Q and P-Q will beA. `90^@`B. between `0^@ and 180^@`C. `180^@` onlyD. None of these

Answer» Correct Answer - B
(P+Q).(P-Q)
`=P^2 + PQ cos theta - PQ cos theta -Q^2`
`=P^2 - Q^2`
Since dot product may be positive (if P> Q),
negative (if Q>P) or zero (if P=Q). Therefore
angle between (P+Q) and (P-Q) may be acute,
obtuse or `90%.`


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