Powers or Trig Functions Question - Integral

In summary, for the integral of (sec x)^5 (tan x)^3 dx, you can use the substitution u = tan(x) for the even power of tan and the identity 1+tan^2x=sec^2x for the odd power of tan. With these hints, the problem can be easily solved.
  • #1
Shkolnikoff
2
0

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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  • #2
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.
 
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  • #3
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
 
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  • #4
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:
 

What is the difference between a power function and a trigonometric function?

A power function is a mathematical expression that involves raising a variable to a fixed exponent, while a trigonometric function is a mathematical function that relates the angles of a triangle to the lengths of its sides. In other words, power functions involve only algebraic operations, while trigonometric functions involve trigonometric ratios such as sine, cosine, and tangent.

What is an integral of a power function?

An integral of a power function is the reverse process of differentiation. It represents the area under the curve of a power function and can be calculated using the fundamental theorem of calculus. The integral of a power function with exponent n is given by (x^(n+1))/(n+1) + C, where C is a constant.

How do you integrate a trigonometric function?

To integrate a trigonometric function, you need to use trigonometric identities and substitution. By substituting the variable with a trigonometric function and using trigonometric identities, the integral can be simplified into a form that can be integrated using basic integration techniques.

What is the purpose of finding the integral of a function?

The purpose of finding the integral of a function is to calculate the area under the curve of the function. This can be useful in many real-life applications, such as calculating the work done by a force, finding the displacement of an object, or determining the total cost of a product based on its rate of change.

Can all functions be integrated?

No, not all functions can be integrated. Some functions are not continuous or have discontinuities, making it impossible to find their integral. However, most elementary functions can be integrated using various integration techniques.

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