Primitive of x/sqrt(4+x^4): Is Substitution Necessary?

  • Context: Undergrad 
  • Thread starter Thread starter esmeco
  • Start date Start date
  • Tags Tags
    Primitive
Click For Summary

Discussion Overview

The discussion revolves around the integration of the function x/sqrt(4+x^4), specifically whether substitution is necessary for solving the integral. Participants explore different methods and approaches to tackle the problem, focusing on techniques relevant to calculus and integration.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests that substitution is required but questions the applicability of standard substitution rules due to the presence of x^4 instead of x^2.
  • Another participant proposes a substitution of u = x^2, leading to a transformation of the integral into a form involving inverse hyperbolic functions.
  • A different participant recommends substituting x^2 with t, indicating an alternative approach to the problem.
  • One participant later argues that substitution may not be necessary and proposes a method involving multiplying the fraction by 1/4 to reformulate the integral, suggesting a potential solution involving arcsin.

Areas of Agreement / Disagreement

Participants express differing opinions on the necessity of substitution, with some advocating for it while others believe it may not be required. The discussion remains unresolved regarding the best approach to solve the integral.

Contextual Notes

Participants do not fully agree on the applicability of substitution methods, and there are various interpretations of how to manipulate the integral. The discussion reflects uncertainty about the transformation of the integral into a solvable form.

esmeco
Messages
144
Reaction score
0
I know that tu solve this primitive we have tu use the substitution method,but I think that none of the rules that should be used apply to this!The problem is, to use the substitution: x=a/b sen t we should have the function in the format (sqrt(a^2 - b^2*x^2)),but instead of a x^2 I have a x^4.
I'm studying for an exam about primitives I'm having tomorrow and I really could use some help on this!
Thanks in advance for the reply!
 
Physics news on Phys.org
Let u = x^2
du/dx = 2x
du = 2xdx

Hence 1/2 Integral (1/ Root( u^2 + 4) ) du
Which is a inverse hyperbolic integral.
 
Make the substitution [itex]x^2 =t[/itex].

Daniel.
 
Now that i look at the primitive,I think it's not necessary to make substitutions...Multyplying the fraction by 1/4 it could be something like: 1/4*x/sqrt(1/4 + (1/4x)^4),which in turn would loook like: 1/4primitive x/sqrt(1/4 + (1/2x^2)2).Since it's no the form f'/sqrt(1-f^2) , the primitive of the function would be: 1/4arcsen(1/2x^2).
Could this be solved this way?
Thanks in advance for the reply!^_^
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 7 ·
Replies
7
Views
12K
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K