Can I use brackets on the subscript of a log?

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In summary, the brackets around the subscript of a log mean that you can include them to make the meaning of the expression multiply where it shouldn't. The parentheses won't hurt anything.
  • #1
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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  • #2
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:
 
  • #3
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
 
  • #4
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.
 
  • #5
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]
 
  • #6
Oh great, thanks to both of you.
 

FAQ: Can I use brackets on the subscript of a log?

Can I use brackets on the subscript of a log?

Yes, you can use brackets on the subscript of a log. In fact, brackets are commonly used in the notation for logarithms to indicate the base of the logarithm. For example, the base 10 logarithm of 100 can be written as log10(100) or as log10100.

What is the purpose of using brackets on the subscript of a log?

The purpose of using brackets on the subscript of a log is to indicate the base of the logarithm. This is important because the value of a logarithm is dependent on its base. For example, log10(100) is equal to 2 because 10 raised to the power of 2 is equal to 100. However, log2(100) is equal to approximately 6.644 because 2 raised to the power of 6.644 is approximately equal to 100.

Can I use any base for the logarithm?

Yes, you can use any base for the logarithm. The most commonly used bases are 10, e (Euler's number), and 2, but any positive value can be used as the base for a logarithm. In fact, logarithms with different bases can be converted into one another using the change of base formula.

How do I evaluate a logarithm with brackets on the subscript?

To evaluate a logarithm with brackets on the subscript, you can use the definition of a logarithm. For example, if you want to evaluate log2(8), you can rewrite it as 2x = 8 and solve for x. In this case, x would be equal to 3, so log2(8) = 3.

Can I use brackets on the subscript of a log in scientific notation?

Yes, you can use brackets on the subscript of a log in scientific notation. In fact, it is common to use scientific notation when dealing with very large or very small numbers in logarithms. For example, the base 10 logarithm of 1,000,000 can be written as log10(1 x 106) or as log10(1.0 x 106).

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