Evaluating Definite Integrals with Floor Function

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SUMMARY

The evaluation of the definite integrals $$\displaystyle \int_{0}^{\pi}\lfloor \cot x \rfloor dx$$ and $$\displaystyle \int_{0}^{\pi}\lfloor \cos x \rfloor dx$$ utilizes the floor function, denoted as $$\lfloor x \rfloor$$. The integral $$\displaystyle \int_{0}^{\pi} \lfloor \cot x \rfloor dx$$ is transformed into a telescopic sum, resulting in a final value of $$-\frac{\pi}{2}$$. This approach also includes the equivalence of the cotangent and tangent functions across specified intervals, demonstrating the improper nature of the integral.

PREREQUISITES
  • Understanding of definite integrals
  • Familiarity with the floor function notation
  • Knowledge of trigonometric functions, specifically cotangent and tangent
  • Basic calculus concepts, including limits and improper integrals
NEXT STEPS
  • Study the properties of the floor function in calculus
  • Learn about improper integrals and their evaluation techniques
  • Explore the relationship between cotangent and tangent functions
  • Investigate telescoping series and their applications in integral evaluation
USEFUL FOR

Mathematicians, calculus students, and educators interested in advanced integral evaluation techniques, particularly those involving the floor function and trigonometric identities.

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Evaluation of $$\displaystyle \int_{0}^{\pi}\lfloor \cot x \rfloor dx$$ and $$\displaystyle \int_{0}^{\pi}\lfloor \cos x \rfloor dx\;,$$ where $$\lfloor x \rfloor $$ denote Floor function of $$x$$
 
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jacks said:
Evaluation of $$\displaystyle \int_{0}^{\pi}\lfloor \cot x \rfloor dx$$ and $$\displaystyle \int_{0}^{\pi}\lfloor \cos x \rfloor dx\;,$$ where $$\lfloor x \rfloor $$ denote Floor function of $$x$$

[sp]By treating the integral as 'improper' You obtain a telescopic sum...

$\displaystyle \int_{0}^{\pi} \lfloor \cot x \rfloor dx = \int_{- \frac{\pi}{2}}^{\frac{\pi}{2}} \lfloor \tan x \rfloor dx = \lim_{n \rightarrow \infty} \tan^{-1} 0 - \tan^{-1} 1 + \tan^{-1} 1 - \tan^{-1} 2 + ... + \tan^{-1} (n-1) - \tan^{-1} n = - \frac{\pi}{2}$ [/sp]

Kind regards

$\chi$ $\sigma$
 

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