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Logarithmic function: Calculus help?

Find the derivative of the function... These are the last few questions on my homework that i didn't understand. Any help will be great thank you.

1. y= t ln sqrt t

2. y= ln x/1+ln x

3. y = theta sin (ln theta)

2 Answers

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  • ?
    Lv 7
    9 years ago

    1) y = t ln (√t)

    y = t (1/2) ln t = 1/2 t ln t

    dy/dt = (1/2) d/dt [ t ] * ln (t )+ t d/dt [ ln (t) ] Product rule

    dy/dt = (1/2)(1 * ln (t) + t (1/t ))

    dy/dt = (1/2) (ln (t) + 1)

    2) y = ln (x ) /( 1 + ln x) Parentheses matter

    dy/dx = ( d/dx [ ln (x)] * (1 + ln x) - ln (x) * d/dx [1 + ln x] ) / (1 + ln x)^2

    Quotient Rule

    dy/dx = ( (1/x)(1 + ln x) - ln x (1/x)) / ((1 + ln x)^2

    dy/dx = (1/x) / (1 + ln x)^2

    dy/dx = / (x (1 + ln x)^2)

    3)Let x = theta

    y = x sin (ln x)

    dy/dx = d/dx [x] * sin (ln x) + x * d/dx [sin (ln x) ] Product rule

    dy/dx = sin (ln x) + x * [cos (ln x) d/dx (ln x) ] Chain rule

    dy/dx = sin (ln x) + x * [ cos (ln x) * (1/x) ]

    dy/dx = sin (ln x) + cos (ln x)

  • 9 years ago

    I can solve it here, but it will be messy. Try wolframalpha. It shows u how to do it step by step too. wolfram is ur best friend in math. but if u rely on it too much u will fail :P

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