Log Identity Proofs: Simplifying a^{log_{b}(c)}=c^{log_{b}(a)}

In summary, the conversation discusses the steps to simplify the expression a^{log_{b}(c)}=c^{log_{b}(a)}, where the attempt at a solution involves taking log_{a} of both sides and using the commutative law of multiplication to simplify the right-hand side. The goal is to simplify the right-hand side to become log_{b}c.
  • #1
K29
108
0

Homework Statement



[itex]a^{log_{b}(c)}=c^{log_{b}(a)}[/itex]


The Attempt at a Solution


Take [itex]log_{a}[/itex] of both sides:
[itex]log_{a}(a^{log_{b}(c)})=log_{a}(c^{log_{b}(a)})[/itex]

gives:
[itex]log_{b}c=log_{b}alog_{a}c[/itex]

Looks like one more step for the RHS. I sort of see that the RHS should become [itex]log_{b}c[/itex] and then we'll be done. But standard log laws don't seem to help me make this step. Please help with this step/explain why this is so?
 
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  • #2
K29 said:

Homework Statement



[itex]a^{log_{b}(c)}=c^{log_{b}(a)}[/itex]


The Attempt at a Solution


Take [itex]log_{a}[/itex] of both sides:
[itex]log_{a}(a^{log_{b}(c)})=log_{a}(c^{log_{b}(a)})[/itex]

gives:
[itex]log_{b}c=log_{b}alog_{a}c[/itex]

Looks like one more step for the RHS. I sort of see that the RHS should become [itex]log_{b}c[/itex] and then we'll be done. But standard log laws don't seem to help me make this step. Please help with this step/explain why this is so?
Using the commutative law of multiplication, the RHS is [itex]\displaystyle \ (\log_{a\,}c)\,(\log_{b\,}a)\quad\to\quad\log_{b\,}\left(a^{\log_{a\,}c}\right)[/itex]
 
  • #3
Got it. Thanks a bunch
 

Related to Log Identity Proofs: Simplifying a^{log_{b}(c)}=c^{log_{b}(a)}

1. What is a log identity?

A log identity, also known as a logarithmic identity, is an equation involving logarithms that is always true for any value of the variable in the equation. It is similar to a trigonometric identity, but instead of involving trigonometric functions, it involves logarithmic functions.

2. Why is proving a log identity important?

Proving a log identity is important because it helps to establish the validity of mathematical equations involving logarithms. It also allows for the simplification and manipulation of logarithmic expressions, making them easier to solve in more complex equations.

3. What are the steps to prove a log identity?

The steps to prove a log identity may vary, but generally they involve using the properties of logarithms, such as the product rule, quotient rule, and power rule, to manipulate the equation and show that both sides are equal. This is typically done by starting with one side of the equation and manipulating it until it is in the same form as the other side.

4. Are there any common log identities that are frequently used?

Yes, there are several common log identities that are frequently used in mathematics, such as the product rule (log(ab) = log(a) + log(b)), quotient rule (log(a/b) = log(a) - log(b)), power rule (log(a^b) = b*log(a)), and change of base rule (log_b(a) = log_c(a)/log_c(b)). These identities can often be applied to simplify and solve logarithmic equations.

5. What are some tips for proving a log identity?

Some tips for proving a log identity include being familiar with the properties of logarithms, carefully manipulating both sides of the equation, and checking your work by plugging in values for the variables to ensure that both sides are equal. It can also be helpful to work backwards from one side of the equation to the other, using the properties of logarithms to simplify and transform the expression.

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