Derivative of log proof question

In summary, the constant multiple rule is used in differentiating logarithmic functions because the constant term, 1/ln(b), can be factored out and treated as a constant while the logarithmic term, lnx, is differentiated. This is similar to how a constant, such as 2, is treated in differentiation.
  • #1
LearninDaMath
295
0
Proof

d/dx [log[itex]_{b}x[/itex]] = d/dx (lnx/lnb) = 1/lnb d/dx(lnx) = 1/xlnb , when x>0


I think I see the constant multiple rule at work here, but why? Is it because 1/lnb is a constant, so it is "factored" out of lnx/lnb and treated as a constant while lnx is treated as the term to be differentiated?
 
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  • #2
LearninDaMath said:
Proof

d/dx [log[itex]_{b}x[/itex]] = d/dx (lnx/lnb) = 1/lnb d/dx(lnx) = 1/xlnb , when x>0


I think I see the constant multiple rule at work here, but why? Is it because 1/lnb is a constant, so it is "factored" out of lnx/lnb and treated as a constant while lnx is treated as the term to be differentiated?

Exactly. ln(b) is just a constant factor, like 2.
 
  • #3
Dick said:
Exactly. ln(b) is just a constant factor, like 2.

cool thanks
 

What is the derivative of log(x)?

The derivative of log(x) is 1/x.

How do you prove the derivative of log(x)?

To prove the derivative of log(x), we can use the definition of the derivative, which is the limit as h approaches 0 of (f(x+h)-f(x))/h. By plugging in log(x+h) and log(x) into this formula and simplifying, we can show that the derivative of log(x) is 1/x.

What is the chain rule for derivatives?

The chain rule for derivatives states that the derivative of f(g(x)) is equal to f'(g(x)) * g'(x), where f'(x) is the derivative of the outer function and g'(x) is the derivative of the inner function.

Can the derivative of log(x) be negative?

Yes, the derivative of log(x) can be negative for values of x less than 1. This is because the graph of log(x) is decreasing for x values less than 1, meaning the slope of the tangent line at those points will be negative.

What is the derivative of ln(x)?

The derivative of ln(x) is also 1/x. This is because ln(x) and log(x) are different notations for the same function, the natural logarithm.

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