Can I use brackets on the subscript of a log?

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Homework Help Overview

The discussion revolves around the use of brackets in the subscript of logarithmic expressions, specifically whether including brackets alters the meaning of the logarithm. Participants are exploring the implications of formatting in mathematical notation.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning if using brackets around subscripts or non-subscripts changes the meaning of logarithmic expressions. There are attempts to clarify the implications of formatting choices in mathematical writing.

Discussion Status

Some participants have expressed confusion regarding the relevance of certain proofs shared in the thread. However, there is a general inclination towards accepting the use of brackets without concern for negative implications on meaning.

Contextual Notes

There are concerns about clarity in mathematical notation, particularly when writing in software like Word, where subscripts may not visually represent fractions clearly. Participants are also navigating the balance between mathematical rigor and personal preference in notation.

priceofcarrot
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Hi, can I type brackets around the subscript of a log? Can I type brackets around the non subscript as well?

I included what I mean in the picture below, as it's maybe easier to see what I mean. I'm just concerned that the meaning of what I wrote changes when I include the brackets. I don't want it to now mean multiplied where it shouldn't.


Do both forms mean the same thing? Thanks
 

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I wouldn't bother with the brackets, just make sure that if you're writing out the subscripts on paper that it's obvious which is which.

By the way, take a look at this proof:

[tex]\log_ab=x[/tex]
This is equivalent to
[tex]a^x=b[/tex]
Now, the LHS can become
[tex]\frac{1}{a^{-x}}=\left(\frac{1}{a}\right)^{-x}[/tex]
Hence we can use the definition of the log again to transform it back into
[tex]\log_{1/a}b=-x[/tex]

:wink:
 
Sorry, but why did you include that? I'm just confused. I appreciate it though.

Anyway, I'd like to use the brackets if possible, just because when I write my calculations in Word, a subscript '1/3' looks kind of weird to me, because it doesn't look like 1 over 3.

Thanks
 
priceofcarrot said:
Sorry, but why did you include that? I'm just confused. I appreciate it though.

Anyway, I'd like to use the brackets if possible, just because when I write my calculations in Word, a subscript '1/3' looks kind of weird to me, because it doesn't look like 1 over 3.

Thanks

The parentheses won't hurt anything. Go ahead and use them.
 
priceofcarrot said:
Sorry, but why did you include that? I'm just confused. I appreciate it though.

Because if [tex]\log_ab=x[/tex] and [tex]\log_{1/a}b=-x[/tex] then [tex]\log_{1/a}b=-\log_ab[/tex] hence you can change your log expressions from [itex]\log_{1/7}3[/itex] to [itex]-\log_73[/itex]
 
Oh great, thanks to both of you.
 

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