Finding the Limit of a Complex Expression

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SUMMARY

The limit of the expression lim_{x \rightarrow 1} (2-x)^{tan \frac{\pi x}{2}} is evaluated using logarithmic transformation and l'Hôpital's rule. The correct limit is found to be e^{2/\pi}, not e^{\pi/2} as initially proposed. This conclusion is supported by numerical verification using values close to x=1, which yield results around 1.89. The discrepancy arises from misapplication of l'Hôpital's rule in the original attempt.

PREREQUISITES
  • Understanding of limits in calculus
  • Familiarity with l'Hôpital's rule
  • Knowledge of logarithmic functions
  • Basic trigonometric functions and their limits
NEXT STEPS
  • Review the application of l'Hôpital's rule in limit problems
  • Study the properties of logarithmic limits
  • Explore the behavior of trigonometric functions near their limits
  • Practice evaluating limits involving exponential functions
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Students studying calculus, particularly those focusing on limits and l'Hôpital's rule, as well as educators looking for examples of limit evaluation techniques.

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'hospital's 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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Check your l'Hopital's rule again. I get 2/pi, not pi/2.
 
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.
 

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