Thursday, December 15, 2011

Trig Integration Problem: Integral of (sin(x))^3/tan(x)

To find the following indefinite integral:





May be written as: Integrate or integral of (Sin(x))^3/(tan(x)) or Integrate or integral of (sin(x))^3/tan(x)

Follow these steps:


  
We are trying to get this into a form where we can do u substitution. This is done by using trig identities and rewriting the integral.

First, rewrite this a (sin(x))^3/1 divided by sin(x)/cos(x):

Simplified from above:

Simplified further by dividing the sin(x) we now have this simplified integral:

Substitution can now be used. We see that if we let u=sin(x) this makem du=cos(x)dx. This takes care of the sin and the cos.


The integral rewritten with the u substitution:

Performing the integration with respect to u:

Now replacing our u with the value we specified above gives us our final answer of (1/3)(sin(x))^3 + C.


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