# Evaluating log

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• Dec 18th 2011, 03:34 PM
Bashyboy
Evaluating log
If log_b 6 = .4040 then b^-.4040 is equal to...I am not to sure about how to solve this.
• Dec 18th 2011, 03:37 PM
Plato
Re: Evaluating log
Quote:

Originally Posted by Bashyboy
If log_b 6 = .4040 then b^-.4040 is equal to...I am not to sure about how to solve this.

If $\log_b(X)=a$ then $b^a=X~.$
• Dec 18th 2011, 04:10 PM
Bashyboy
Re: Evaluating log
Well, the exponent on b is negative, does that change the definition you gave me at all?
• Dec 18th 2011, 04:14 PM
Plato
Re: Evaluating log
Quote:

Originally Posted by Bashyboy
Well, the exponent on b is negative, does that change the definition you gave me at all?

No indeed. It just requires one more step.

If $b^a=X$ then $b^{-a}=\frac{1}{X}~.$
• Dec 18th 2011, 04:28 PM
Bashyboy
Re: Evaluating log
Oh, yes--I undserstand now. I do have another one, though: If log 2 = .3010 then log sqroot(20) is equal to.
• Dec 18th 2011, 04:44 PM
Plato
Re: Evaluating log
Quote:

Originally Posted by Bashyboy
Oh, yes--I undserstand now. I do have another one, though: If log 2 = .3010 then log sqroot(20) is equal to.

First, you should start a new thread for a new question.

Note that $\log(\sqrt{a})=\tfrac{1}{2}\log(a)$.

$\log(20)=\log(10)+\log(2)$

Now contrary to modern trends it seems that here $\log$ means $\log_{10}$ so $\log(10)=1$.
• Dec 18th 2011, 04:57 PM
Bashyboy
Re: Evaluating log
Do I sense condescension in your writing, or am I thoroughly mistaken?
• Dec 18th 2011, 05:33 PM
Plato
Re: Evaluating log
Quote:

Originally Posted by Bashyboy
Do I sense condescension in your writing, or am I thoroughly mistaken?

You either have the largest chip on your shoulder or you can't read.
Are you angry at me for not giving a complete and polished solution?
Do you not want to learn how to do these?
• Dec 18th 2011, 05:49 PM
Bashyboy
Re: Evaluating log
No, I am absolutely not angry. I inferred that impression on my first reading of your post; but, after re-reading it, I have found that impression to be wrong. I am terrible sorry. I sensitive when it comes to scorning my mathematical knowledge; and I know it is scarce, due to myself having studied it a little later in life than normal, and that is why I was a bit jumpy. Again, sorry.