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Math Help - Tricky derivative problem!

  1. #1
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    Tricky derivative problem!

    I understand how to take the derivative of an equation with respect to a variable, say S, but what do I do when there are two variables involved? Here's the problem d/dx [3cos(x^2) - 4e^t]
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  2. #2
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    Re: Tricky derivative problem!

    Treat t as constant, so
    d/dx [3cos(x^2) - 4e^t]
    = 3 d/dx cos(x^2) - 4 d/dx e^t
    = -6x sin(x^2) - 4e^t x
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  3. #3
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    Re: Tricky derivative problem!

    Quote Originally Posted by Kanwar245 View Post
    Treat t as constant
    Correct. But then...

    , so

    d/dx [3cos(x^2) - 4e^t]
    = 3 d/dx cos(x^2) - 4 d/dx e^t
    ... the e^t is constant, so it might as well come out with the 4:

    = 3 d/dx cos(x^2) - 4e^t d/dx 1

    ... but then the whole second term is a constant term and drops out...

    = -6x sin(x^2)

    ... period.

    As long as t isn't a function of x, or anything... the context of the problem here would help.
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  4. #4
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    Re: Tricky derivative problem!

    What would it look like if t was a function of x?
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  5. #5
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    Re: Tricky derivative problem!

    my bad, I integrated the 2nd part!
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  6. #6
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    Re: Tricky derivative problem!

    Quote Originally Posted by NotAMathmatician314 View Post
    What would it look like if t was a function of x?
    then you'd need to use the chain rule.
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