Find the limit of ln (sinx) as x approaches pi

In summary, the conversation discusses finding the limit of ln(sin(x)) as x approaches pi- and the appropriate method to use. The squeeze theorem is considered but it is determined that finding the limit as sin(x) approaches 0 is a simpler approach. The suggestion to graph the function is mentioned as a helpful tool.
  • #1
essedbl
3
0
I need to find the limit of. Ln (sinx) as x approaches pi-, that is, as x approaches pi from the left.

I thought I should use the squeeze theorem, but I am not sure how to apply it. My teacher is not requiring us to use the delta/Epsilon method, so I am sure it is a squeeze method. But how do I set it up?

I tried -1 < sinx < 1,
Thus ln (-1) < ln (sinx) < ln (1)

But you can't take the ln of a negative... please help.
 
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  • #2
What can you say about [itex]\sin(x)[/itex] as [itex]x \rightarrow \pi^-[/itex]? Is it positive or negative? What value does it approach?
 
  • #3
As x aproaches pi from the left your sine function aproaches 0. This means this is equivalent of finding the limit as the thing inside the natural log aproaches 0. Its very easy limit.
 
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  • #4
Oh. So this isn't squeeze action... I just find the limit of ln as sinx approaches zero. Hmm... I would need to graph that. But that should be simple enough. Tjanks guys
 
  • #5
essedbl said:
Oh. So this isn't squeeze action... I just find the limit of ln as sinx approaches zero. Hmm... I would need to graph that.
Good idea. Remember that x is approaching π from the left, which says something about how sin(x) is approaching zero, and finally, what ln(sin(x)) is doing.
essedbl said:
But that should be simple enough. Tjanks guys
 

1. What is the limit of ln (sinx) as x approaches pi?

The limit of ln (sinx) as x approaches pi is undefined.

2. Why is the limit of ln (sinx) as x approaches pi undefined?

The limit is undefined because the function ln (sinx) is not defined at x = pi. As x approaches pi, the value of sinx approaches 0, which is not within the domain of ln (x).

3. Can the limit of ln (sinx) as x approaches pi be evaluated using L'Hopital's rule?

No, L'Hopital's rule can only be used for indeterminate forms such as 0/0 or infinity/infinity. As the limit of ln (sinx) as x approaches pi is undefined, it cannot be evaluated using L'Hopital's rule.

4. Is the limit of ln (sinx) as x approaches pi equal to zero?

No, the limit is not equal to zero. As x approaches pi, the value of ln (sinx) approaches positive infinity.

5. How can we graphically represent the limit of ln (sinx) as x approaches pi?

The limit of ln (sinx) as x approaches pi can be represented graphically as a vertical asymptote at x = pi. This means that the function approaches infinity as x approaches pi from both the left and right sides.

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