How do I solve an indefinite integral with a trigonometric substitution?

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In summary, to find the indefinite integral of 1/[(x^4)(sqrt(9x^2 -1))], we can use the substitution x=3secy and dx=3secytanydy to convert the top function to an integral of [3secytanydy]/[(tany)(3secy)^4]. Then, we can label the triangle with hypotenuse = 3x, adjacent side = 1, and opposite side = sqrt(9x^2 - 1) with angle t. Using this, we can simplify the integral to \int \frac{1/3 sec(t)tan(t)dt}{(1/3)^4 sec^4(t)~tan
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mat331760298
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1. indefinite integral of 1/[(x^4)(sqrt(9x^2 -1))]

I'm looking for step by step help here. I use x=3secy and dx=3secytanydy to convert the top function to integral of: [3secytanydy]/[(tany)(3secy)^4]

I am not sure if this is right/how to get further
 
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mat331760298 said:
1. indefinite integral of 1/[(x^4)(sqrt(9x^2 -1))]

I'm looking for step by step help here. I use x=3secy and dx=3secytanydy to convert the top function to integral of: [3secytanydy]/[(tany)(3secy)^4]

I am not sure if this is right/how to get further

I labelled by triangle with hypotenuse = 3x, adjacent side = 1, opp. side = sqrt(9x^2 - 1), with angle t.

So sec t = 3x ==> x = 1/3 sec t
dx = 1/3 sec t * tan t * dt
sqrt(9x^2 -1) = tan t

Then,
[tex]\int \frac{dx}{x^4 \sqrt{9x^2 - 1}} = \int \frac{1/3 sec(t)tan(t)dt}{(1/3)^4 sec^4(t)~tan(t)}[/tex]
Can you continue from there?
 
  • #3


do you get integral of:27*(cost)^3 dt ?
 
  • #5


then you integrate to get 27(sint-(1/3)(sint)^3) and use opp side over hypotenuse to replace with sint?
 
  • #6


Yes. After you get the antiderivative, undo your substitution, and you'll be done.
 

What is an integral?

An integral is a mathematical concept that represents the area under a curve in a graph. It is used to calculate the total value of a function over a specific interval or range.

How do you solve an integral?

To solve an integral, you can use a variety of methods such as integration by parts, substitution, or partial fractions. The most common method is using the fundamental theorem of calculus, which involves finding the antiderivative of the function and then evaluating it at the upper and lower limits of the integral.

What is step by step help?

Step by step help is a method of breaking down a problem into smaller, more manageable steps in order to help understand and solve it. In the context of integrals, step by step help involves breaking down the process of solving an integral into smaller, easier to understand steps in order to guide someone through the process.

Why is it important to show each step in solving an integral?

Showing each step in solving an integral is important because it helps to understand the process and identify any mistakes made along the way. It also allows for a more thorough understanding of the concept and helps to build a strong foundation for future problems.

What are some tips for solving integrals?

Some tips for solving integrals include understanding the properties and rules of integration, practicing with a variety of problems, and breaking down the integral into smaller parts if necessary. It is also helpful to double check your work and use resources such as textbooks or online tutorials for additional guidance.

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