# Domain Problem

• Sep 22nd 2008, 03:22 PM
dm10
Domain Problem
What's the domain of G(t) = ln(t^4-1)?

How did you get the answer, the answer in the book says that it's (-infinity, -1) union (1, infinity) but I don't really understand why.
• Sep 22nd 2008, 03:35 PM
Plato
For $\displaystyle x \in \left[ { - 1,1} \right]\quad \Rightarrow \quad \ln \left( {x^4 - 1} \right) \mbox{ is meaningless!}$
• Sep 22nd 2008, 03:38 PM
dm10
Quote:

Originally Posted by Plato
For $\displaystyle x \in \left[ { - 1,1} \right]\quad \Rightarrow \quad \ln \left( {x^4 - 1} \right) \mbox{ is meaningless!}$

What?
• Sep 22nd 2008, 04:55 PM
Plato
Quote:

Originally Posted by dm10
What?

dn10, you have a very hard road of learning ahead of you if you truly want to understand this material.
You should pay more attention to basic definitions.
Of course, if you could care less then forget it.
• Sep 22nd 2008, 05:39 PM
Krizalid
$\displaystyle t^{4}-1=\left( t^{2}+1 \right)\left( t^{2}-1 \right)>0,$ this last 'cause logarithm is defined for numbers greater than zero. Hence, it remains to solve $\displaystyle t^2-1>0$ which gives the expected answer.