Antiderivative of Sin^3(x)Cos^4(x): Solutions & Examples

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In summary, the conversation involves a student struggling with computing the antiderivative of sin^3(x)cos^4(x) dx and seeking help from others on how to approach the problem. The solution involves using integration by parts and a substitution of u = cos(x) to simplify the integral to u^6 - u^4. The importance of finding the correct substitution is emphasized.
  • #1
tunabeast
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Homework Statement


Compute the following antiderivative [tex] \int (sin^3(x))(cos^4(x)) dx [/tex]


Homework Equations





The Attempt at a Solution


If this problem requires use of integration by parts I'm struggling to work out to split it up and make it manageable. Have searched countlessly for a similar example on the net but have had no luck. Thanks
 
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  • #2
There is a standard "method" when you have a trig function to an odd power.

Since sin(x) it to the 3rd power, take one out to use with dx, convert sin2(x) to cos:
[tex]\int sin^3(x)cos^4(x)dx= \int sin^2(x)cos^4(x) sin(x)dx= \int (1- cos^2(x))cos^4(x) sin(x)dx[/itex]
Now what substitution will make that easy?
 
  • #3
All you should do is new variable u = cos(x). You'll get integral u^4-u^6.
 
  • #4
Actually, [tex]u^6 - u^4[/tex] due to the negative in the derivative of [tex]cos(x)[/tex]
 
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  • #5
fikus what do you mean, i can do a substitution straight away?
 
  • #6
tunabeast said:
fikus what do you mean, i can do a substitution straight away?
you can once you find that the derivative of your substitution appears in your original problem
 
  • #7
tunabeast said:
fikus what do you mean, i can do a substitution straight away?
I believe that is what everyone as been trying to tell you!
 

1. What is the antiderivative of sin^3(x)cos^4(x)?

The antiderivative of sin^3(x)cos^4(x) is (1/12)sin^4(x) - (1/8)sin^2(x) + (1/48)cos^6(x) + C.

2. How is the antiderivative of sin^3(x)cos^4(x) derived?

The antiderivative can be derived by using the substitution method and the power reduction formula for sin^2(x).

3. Can you provide an example of solving for the antiderivative of sin^3(x)cos^4(x)?

Example: Find the antiderivative of sin^3(x)cos^4(x).
Solution: Let u = sin(x), du = cos(x)dx. Then, we have sin^3(x)cos^4(x)dx = u^3(1-u^2)^2du. Using the power reduction formula for sin^2(x), we get u^3(1-(1/2)sin^2(x))^2du. Expanding and simplifying, we get (1/12)sin^4(x) - (1/8)sin^2(x) + (1/48)cos^6(x)+ C, where C is the constant of integration.

4. Is the antiderivative of sin^3(x)cos^4(x) unique?

Yes, the antiderivative of sin^3(x)cos^4(x) is unique up to a constant of integration.

5. Can the antiderivative of sin^3(x)cos^4(x) be expressed in terms of other trigonometric functions?

No, the antiderivative of sin^3(x)cos^4(x) cannot be expressed in terms of other trigonometric functions. It can only be expressed as a combination of powers of sin(x) and cos(x).

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