Integral of sin^3 dx
The solution
Detail solution
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Rewrite the integrand:
sin3(x)=(1−cos2(x))sin(x)
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There are multiple ways to do this integral.
Method #1
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Let u=cos(x).
Then let du=−sin(x)dx and substitute du:
∫(u2−1)du
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Integrate term-by-term:
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The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
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The integral of a constant is the constant times the variable of integration:
∫(−1)du=−u
The result is: 3u3−u
Now substitute u back in:
3cos3(x)−cos(x)
Method #2
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Rewrite the integrand:
(1−cos2(x))sin(x)=−sin(x)cos2(x)+sin(x)
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Integrate term-by-term:
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The integral of a constant times a function is the constant times the integral of the function:
∫(−sin(x)cos2(x))dx=−∫sin(x)cos2(x)dx
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Let u=cos(x).
Then let du=−sin(x)dx and substitute −du:
∫(−u2)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫u2du=−∫u2du
-
The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
So, the result is: −3u3
Now substitute u back in:
−3cos3(x)
So, the result is: 3cos3(x)
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The integral of sine is negative cosine:
∫sin(x)dx=−cos(x)
The result is: 3cos3(x)−cos(x)
Method #3
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Rewrite the integrand:
(1−cos2(x))sin(x)=−sin(x)cos2(x)+sin(x)
-
Integrate term-by-term:
-
The integral of a constant times a function is the constant times the integral of the function:
∫(−sin(x)cos2(x))dx=−∫sin(x)cos2(x)dx
-
Let u=cos(x).
Then let du=−sin(x)dx and substitute −du:
∫(−u2)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫u2du=−∫u2du
-
The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
So, the result is: −3u3
Now substitute u back in:
−3cos3(x)
So, the result is: 3cos3(x)
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The integral of sine is negative cosine:
∫sin(x)dx=−cos(x)
The result is: 3cos3(x)−cos(x)
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Now simplify:
6(cos(2x)−5)cos(x)
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Add the constant of integration:
6(cos(2x)−5)cos(x)+constant
The answer is:
6(cos(2x)−5)cos(x)+constant
The answer (Indefinite)
[src]
/
| 3
| 3 cos (x)
| sin (x) dx = C - cos(x) + -------
| 3
/
∫sin3(x)dx=C+3cos3(x)−cos(x)
The graph
3
2 cos (1)
- - cos(1) + -------
3 3
−cos(1)+3cos3(1)+32
=
3
2 cos (1)
- - cos(1) + -------
3 3
−cos(1)+3cos3(1)+32
2/3 - cos(1) + cos(1)^3/3
Use the examples entering the upper and lower limits of integration.