derivative of ln(1/x) vs derivative of 1/ln(x)

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Many calculus students tend to make misteaks when taking the derivative of ln(1/x) vs the derivative of 1/ln(x). For the derivative of ln(1/x), we can actually use a log property to simplify the expression first before taking the derivative so we don't need to use the quotient rule. For the derivative of 1/ln(x), we can write it as (ln(x))^-1 and then use the power rule and the chain rule to find the derivative. Subscribe to @bprpcalculusbasicsfor more calculus tutorials!

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0:28 Yes, I remember the *loy* property

Jaojao_puzzlesolver
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Cool video, learning some calculus right now and I get tripped up with logarithms sometimes. Thanks a lot!

browhat
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Also fun to just use the chain rule on the first one, to check.

Outside derivative: let v = 1/x; d/dv(ln v) = 1/v = 1/(1/x) = x
Inside derivative: d/dx(1/x) = d/dx(x^(-1)) = (-x^(-2)) = -1/(x^2)
Multiply together: x * -1/(x^2) = -x/(x^2) = -1/x

(It was not easy trying to figure out how to write all the steps.)

ZipplyZane
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for y = 1 / ( ln x )
I like to use the chain rule.

Let u = ln x

so y = 1 / u
dy / dx = - 1 / u^2
du / dx = 1 / x

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

michaelempeigne
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Technically doing the chain rule + derivative power rule for ln(1/x) does still work fine albiet over complicating it

SJrad
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My first thought was to use the logarithm rule to simplify ln(a/b) = ln a - ln b, which gives ln(1/x) = ln 1 - ln x = -ln x, then differentiate to obtain -1/x

ElementaryLord
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Can you do more series questions instead of just derivatives and integrals and limits. Show Calc BC kids some love

joser
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I have a request. Can you prove the law of cosines without pethagon
theorem for me? Ever since I learned law of cosines I thought it can be a method to prove pethagon theorem but I just saw a proof of cosines that involves pethagon theorem so using it would be circular reasoning

wristdisabledwriter
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❤ how can i solve for the derivative of ln(1+x)^4

albertomaths
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Hey bprp, what do you think of ln^2(x) notation for power of ln

emmecuh