Cos^2(x) Integral: Get Help Solving

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In summary, the integral of cos^2x can be simplified to (1/2) + (1/4)sin2x, with the help of the identity cos^2x = (1+cos2x)/2. By breaking it into two integrals and using a u-substitution, we can arrive at this solution. Remember to include a +C at the end of the answer.
  • #1
iRaid
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Homework Statement


[itex]\int cos^{2}x dx[/itex]

I know that

[itex]cos^{2}x = \frac{1+cos2x}{2}[/itex]

but I don't see how that helps me.
Can someone help walk me through it..

Homework Equations


The Attempt at a Solution

 
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  • #2
Well, that leaves you with:
[tex]\int \frac{1}{2}+\frac{1}{2}cos(2x)dx[/tex]

Which you can break up into two integrals:
[tex]\int \frac{1}{2}dx + \int \frac{1}{2}cos(2x)dx[/tex]

The first one should be no problem. Isn't there some sort of substitution you can make for the second one?
 
  • #3
Can you integrate cos(2x)? Use a u substitution.
 
  • #4
u=2x du=(1/2)dx
(1/2)∫cosudu
=(1/4)sin2x

So then..
x/2 + (1/4)sin2x
but that's not the answer..
 
Last edited:
  • #5
iRaid said:
u=2x du=(1/2)dx
(1/2)∫cosudu
=(1/4)sin2x

So then..
x/2 + (1/4)sin2x
but that's not the answer..

I think it is the correct answer. You should probably put a +C on it. Is that the problem?
 
  • #6
Dick said:
I think it is the correct answer. You should probably put a +C on it. Is that the problem?

Oh nevermind was looking at the wrong answer. Thanks for the help.
 

What is the integral of cos^2(x)?

The integral of cos^2(x) is (1/2)x + (1/4)sin(2x) + C. This can be derived using integration by parts or by using the trigonometric identity cos^2(x) = (1/2)(1 + cos(2x)).

How do I solve an integral with cos^2(x)?

To solve an integral with cos^2(x), you can use integration by parts or the trigonometric identity cos^2(x) = (1/2)(1 + cos(2x)) to simplify the integral. Then, you can use basic integration techniques such as substitution or integration by parts to find the solution.

Can I use a calculator to solve a cos^2(x) integral?

Yes, most scientific calculators have the ability to solve integrals. However, it is important to understand the steps involved in solving the integral by hand in order to use the calculator correctly.

What are the limits of integration for a cos^2(x) integral?

The limits of integration for a cos^2(x) integral will depend on the specific problem you are trying to solve. They can be given in the problem or you may need to determine them by looking at the graph of the function.

Are there any special cases when solving a cos^2(x) integral?

Yes, there are special cases when solving a cos^2(x) integral. For example, if the limits of integration are from 0 to π/2, the integral simplifies to π/4. Additionally, if the limits of integration are from 0 to π, the integral simplifies to π/2. It is important to be aware of these special cases when solving cos^2(x) integrals.

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