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Vectors

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Joined:	25 May 2008
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9 Jun 2008 07:32:18 IST

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if vecP+vecQ=vecR & vecP-vecQ=vecS,prove |R*R| +|S*S|=2(P*P+Q*Q)

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if vecP+vecQ=vecR & vecP-vecQ=vecS,prove |R*R| +|S*S|=2(P*P+Q*Q)

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Bipin Dubey

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Joined: 23 Jan 2007

Posts: 7942

9 Jun 2008 10:08:25 IST

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If we square both the equations, we get :

R² = P² + Q² + 2(P.Q)

S² = P² + Q² - 2(P.Q)

Adding these two we get :

R² + S² = 2(P² + Q²)

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