Finding the Limit of a Complex Expression

In summary, the conversation discusses finding the limit of (2-x)^{tan(\pi x/2)} as x approaches 1. The attempt at a solution involves using l'Hopital's rule to rewrite the function as ln((2-x)^{tan(\pi x/2)}), which simplifies to e^{\pi/2}. However, after checking with a calculator, it is determined that the correct answer is 2/\pi, not e^{\pi/2}.
  • #1
daniel_i_l
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Homework Statement



Find the limit:
[tex]lim_{x \rightarrow 1} (2-x)^{tan \frac{\pi x}{2}}[/tex]

Homework Equations





The Attempt at a Solution



I first tried to find the limit of ln of the function inorder to turn the power into a multiplication and got:
[tex]lim_{x \rightarrow 1} \frac{ ln(2-x) sin \frac{\pi x}{2}}{cos \frac{\pi x}{2}}[/tex]
Then I used L'hopitals rule and got:
[tex]lim_{x \rightarrow 1} ln( (2-x)^{tan \frac{\pi x}{2}} ) = \pi / 2[/tex]
That means that [tex]lim_{x \rightarrow 1} (2-x)^{tan \frac{\pi x}{2}} = e^{\pi / 2}[/tex]
Is that right? I tried putting in values to my calc and it looks like the answer should be 1?
What did I do wrong?
Thanks.
 
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  • #2
Check your l'Hopital's rule again. I get 2/pi, not pi/2.
 
  • #3
I also get [itex]2/\pi[/itex], and when I put in x=0.9999 on my calculator, the limit and [itex]e^{2/\pi}[/itex] agree to reasonable accuracy, around 1.89, not 1.
 

FAQ: Finding the Limit of a Complex Expression

What is the definition of a limit?

A limit is the value that a function or expression approaches as the input or variable approaches a certain value or point.

Why is finding the limit of a complex expression important?

Finding the limit of a complex expression is important because it allows us to understand the behavior of the function or expression at a specific point. It also helps us determine the continuity, differentiability, and convergence of a function or expression.

What is the process of finding the limit of a complex expression?

The process of finding the limit of a complex expression involves substituting different values into the expression and observing the resulting output. The limit is then determined by examining the behavior of the outputs as the values get closer and closer to the desired point.

What are some common techniques used to find limits of complex expressions?

Some common techniques used to find limits of complex expressions include algebraic manipulation, factoring, rationalization, and the use of trigonometric identities. Additionally, L'Hopital's rule and the Squeeze theorem are useful tools for evaluating limits of more complicated expressions.

Are there any restrictions or limitations when finding the limit of a complex expression?

Yes, there are some restrictions and limitations when finding the limit of a complex expression. For example, the expression must be defined at the desired point, and the limit may not exist if the left and right-hand limits do not agree. Additionally, some expressions may require more advanced techniques or may not have a limit at all.

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