Wize University Calculus 1 Textbook > Derivatives

Derivatives of Logarithmic Functions

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Derivatives of Logarithmic Functions

The Derivative of the Natural Log Function

The derivative of the natural logarithm function f(x)=lnxf(x)=\ln xis

(lnx)=1x\boxed{\quad (\ln x)'=\frac{1}{x}\quad }

The Derivative of General Log Functions

For a given b>0b>0 and b1 b\ne 1, the derivative of the logarithmic function logbx\log_bx is:
(logbx)=1xlnb\boxed{\quad (\log_{b}x)'=\frac{1}{x\ln b}\quad }

Wize Concept
The Product, Quotient, and Chain Rules still apply for Log Derivatives!

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Example: Log Derivatives

Find the derivative of y=ln(2x2)y=\ln (2x^2)

y=4x2x2=2x\displaystyle y'=\frac{4x}{2x^2}=\frac{2}{x}
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Example: Log Derivatives

Find dydx\displaystyle \frac{dy}{dx} for f(x)=log2(x2+2xex)\displaystyle f(x)=\text{log}_{2}\left(x^2+2xe^x\right)


f(x)=2x+2ex+2xexln2(x2+2xex)f'(x)= \dfrac{2x+2e^x+2xe^x}{\ln2(x^2+2xe^x)}
Find dydt\displaystyle \frac{dy}{dt} for y=5log5(log2t)\displaystyle y=5\log_{5}(\log_{2}t).
Find the derivative of y=log3(7xln2)\displaystyle y=\text{log}_3(7x^{\ln2})

Extra Practice