Powers or Trig Functions Question - Integral

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Homework Help Overview

The discussion revolves around the integral of the function (sec x)^5 (tan x)^3 dx, which falls under the subject area of integral calculus, specifically involving trigonometric functions.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses difficulty with substitution in the integral and suggests that it may relate to the powers of trigonometric functions. Some participants propose rewriting the tan cubed term and applying Pythagorean identities, while others mention memorizing integration rules for trigonometric integrals.

Discussion Status

The discussion has seen participants offering hints and strategies for approaching the integral, with guidance on rewriting terms and utilizing identities. The original poster indicates progress in solving the problem following the hints provided, suggesting a productive direction in the conversation.

Contextual Notes

There is an indication of imposed homework rules, as the original poster seeks hints rather than complete solutions. The discussion also highlights the challenge of correctly substituting terms in the integral.

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Homework Statement


Integral of : (sec x)^5 (tan x)^3 dx


Homework Equations


I am having trouble substituting correctly for this equation and i can't get it to work. I believe it has to do with trig powers ?

If anyone could help be step by step. or even just a hint on how to solve it that would be great.

Thanks in advance !
 
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Welcome to PF!

My Hint would be to rewrite the tan cubed term in terms of a square and a linear, then change the square term with a Pythagorean identity, expand and see where that takes you.
 
Last edited:
You should probably memorize this rule for integrating trigonometric integrals

For any [tex]\int{tan^{m}xsec^{n}xdx}[/tex]

If n is even, substitute u = tan(x)
If m is odd, substitute u = sec(x)
If m is even, n is odd, reduce to powers* of sec(x)
Also, using the identity [tex]1+tan^{2}x=sec^{2}x[/tex] is helpful in all three cases
 
Last edited:
Thank you very much for all your help. I just finished solving the problem.

Its a lot easier using the hints you provided! Thanks!:smile:
 

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