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Homework Help: Proving Formula in Vector Differentiation

  1. Aug 13, 2008 #1
    1. The problem statement
    The formula that must be proven is:
    d (A∙B) = A∙dB + dA∙B
    du du du

    2. The attempt at a solution
    When I substitute the left side of the equation to the general formula of vector differentiation, I got the left side of the equation + ΔA∙ΔB
    Now my only problem is that how can I prove that ΔA∙ΔB = 0 so that it will result to the above equation? Is there any identity in vector differentiation that is ΔA∙ΔB = 0?
  2. jcsd
  3. Aug 13, 2008 #2


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    Science Advisor

    First, what are [itex]\Delta A[/itex] and [itex]\Delta B[/itex]? The "general formula of vector differentiation" that I know involves limits. What limits are you taking?
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