Is There a Way to Integrate ∫xarctanx dx Without Going Back into Arctanx?

  • Thread starter Thread starter Pyroadept
  • Start date Start date
  • Tags Tags
    Integration
Click For Summary
SUMMARY

The discussion focuses on the integration of the function ∫xarctanx dx using integration by parts. The user successfully identifies u = arctanx and dv = x dx, leading to the equation ∫u dv = arctanx(1/2)x^2 - (1/2)∫x^2/(1 + x^2) dx. The challenge presented is to solve the resulting integral without reverting to arctanx, which would negate progress. The solution involves applying long division to simplify the integral x^2/(1 + x^2) into 1 - 1/(1 + x^2).

PREREQUISITES
  • Understanding of integration by parts
  • Familiarity with the derivative of arctanx
  • Knowledge of polynomial long division
  • Basic integration techniques
NEXT STEPS
  • Study the method of integration by parts in depth
  • Learn about polynomial long division techniques
  • Explore advanced integration techniques involving arctan functions
  • Practice solving integrals that involve products of functions
USEFUL FOR

Students studying calculus, particularly those focusing on integration techniques, as well as educators looking for examples of integration by parts and polynomial long division applications.

Pyroadept
Messages
82
Reaction score
0

Homework Statement


∫xarctanx dx


Homework Equations


d/dx (arctanx) = 1/(1 + x^2)
∫1/(1 + x^2) = arctanx
∫u dv = uv - ∫v du

The Attempt at a Solution


Hi everyone,

Here's what I've done so far:

Use integration by parts:
u = arctanx
du = 1/(1 + x^2) dx

dv = x dx
v = (1/2)x^2

∫u dv = uv - ∫v du
= arctanx(1/2)x^2 - (1/2)∫x^2/(1 + x^2) dx

But how do you integrate this new integral without going back into arctanx, in which case you'll be left with zero?

Thanks for any help
 
Physics news on Phys.org
Long division. \frac{x^2}{1+x^2}=1-\frac{1}{1+x^2}
 

Similar threads

Replies
19
Views
3K
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
6
Views
2K
  • · Replies 22 ·
Replies
22
Views
3K
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K