How Do You Use Reduction Formulae for tan^n x?

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SUMMARY

The discussion focuses on the application of reduction formulae for integrating powers of tangent, specifically $$\int\tan^n x\,dx$$. The correct formula is established as $$\int\tan^n x\,dx = \frac{\tan^{n-1} x}{n - 1} - \int\tan^{n-2} x\,dx$$. An example using $$n=4$$ illustrates the process, resulting in $$\int\tan^4 x\,dx = \frac{1}{3}\tan^3 x - \tan x + x + C$$. This example demonstrates the step-by-step application of the reduction formula to simplify the integration of higher powers of tangent.

PREREQUISITES
  • Understanding of integral calculus
  • Familiarity with trigonometric functions, particularly tangent
  • Knowledge of integration techniques, including substitution
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the derivation of the reduction formula for trigonometric integrals
  • Practice integrating other powers of tangent using the established formula
  • Explore related reduction formulae for sine and cosine functions
  • Learn about advanced integration techniques, such as integration by parts
USEFUL FOR

Students and educators in mathematics, particularly those focusing on calculus and trigonometry, as well as anyone seeking to improve their skills in integrating trigonometric functions.

shamieh
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Can someone show me how I would "use" the reduction formulae for $$tan^n x$$ ? I just want to see an example on when I would ever use it. A simple one will do.$$\frac{tan^{n-2}x}{n - 1} - \int tan^{n-2} x dx$$
 
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Hello, shamieh!

Your formula is incorrect.

\int\tan^n\!x\,dx \;=\;\frac{\tan^{n-1}\!x}{n - 1} - \int\tan^{n-2}\!x\,dxExample: .\int\tan^4\!x\,dx

Substitute n=4 into the formula:

\int\tan^4\!x\,dx \;=\;\tfrac{1}{3}\tan^3\!x - \int \tan^2\!x\,dx

. . . . . . . . . =\;\tfrac{1}{3}\tan^3\!x - \int(\sec^2\!x -1)\,dx

. . . . . . . . . =\;\tfrac{1}{3}\tan^3\!x - \int\sec^2\!x\,dx + \int dx

. . . . . . . . . =\;\tfrac{1}{3}\tan^3\!x - \tan x + x + C
 
Thank you sororaban! Also thank you for the PM the other day!
 

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