Finding an antiderivative using substitution rule

In summary, to find the antiderivative of [sec(2x)tan(2x)], you can substitute u=sec(2x) and then use (1/2)du=sec(2x)tan(2x)dx. This will lead to the correct answer.
  • #1
h_k331
33
0
I'm trying to find the antiderivative of [sec(2x)tan(2x)], I can't figure out what part I should be substituting. Any help is appreciated.

Thanks,
hk
 
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  • #2
[tex]
\sec \left( {2x} \right)\tan \left( {2x} \right) = \frac{{\sin \left( {2x} \right)}}{{\cos ^2 \left( {2x} \right)}}
[/tex]

You should be able to finish it off.
 
  • #3
replace 2x by u and you have secu 's derivative under the integral sign
 
  • #4
I ended up working on it some more and came up with u=sec(2x).
Then (1/2)du=sec(2x)tan(2x)dx. I'm not sure if this is the preferred method but it came out to the correct answer.

hk
 
  • #5
Looks good to me!
 
  • #6
Thank you for the replys.

hk
 

1. "What is the substitution rule for finding antiderivatives?"

The substitution rule, also known as u-substitution, is a method used to find antiderivatives of functions that can be written in the form of f(g(x)) * g'(x). The rule states that if we have an integral of the form ∫f(g(x)) * g'(x) dx, we can make a substitution u = g(x) to rewrite the integral as ∫f(u) du.

2. "When should I use the substitution rule for finding antiderivatives?"

The substitution rule is most useful when the integrand contains a composition of functions, such as f(g(x)) * g'(x). In these cases, the substitution rule can simplify the integral and make it easier to solve.

3. "How do I choose the right substitution for finding an antiderivative?"

When choosing a substitution, it is important to look for a function that appears within the integrand and its derivative also appears. The function u = g(x) should also be easy to integrate. It may take some trial and error to find the right substitution, but with practice, it becomes easier.

4. "Can I always use the substitution rule to find an antiderivative?"

No, the substitution rule can only be used for certain types of integrals. It is not applicable to all integrals and sometimes other methods, such as integration by parts, may be necessary to find an antiderivative.

5. "Are there any common mistakes when using the substitution rule for finding antiderivatives?"

One common mistake is forgetting to substitute back in the original variable. Another mistake is choosing the wrong substitution, resulting in a more complicated integral. It is also important to pay attention to any constants or coefficients when making the substitution.

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