Integral of x*sin(2*x) dx
The solution
Detail solution
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There are multiple ways to do this integral.
Method #1
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Use integration by parts:
∫udv=uv−∫vdu
Let u(x)=x and let dv(x)=sin(2x).
Then du(x)=1.
To find v(x):
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There are multiple ways to do this integral.
Method #1
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Let u=2x.
Then let du=2dx and substitute 2du:
∫4sin(u)du
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The integral of a constant times a function is the constant times the integral of the function:
∫2sin(u)du=2∫sin(u)du
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The integral of sine is negative cosine:
∫sin(u)du=−cos(u)
So, the result is: −2cos(u)
Now substitute u back in:
−2cos(2x)
Method #2
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The integral of a constant times a function is the constant times the integral of the function:
∫2sin(x)cos(x)dx=2∫sin(x)cos(x)dx
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Let u=cos(x).
Then let du=−sin(x)dx and substitute −du:
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The integral of a constant times a function is the constant times the integral of the function:
∫(−u)du=−∫udu
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The integral of un is n+1un+1 when n=−1:
∫udu=2u2
So, the result is: −2u2
Now substitute u back in:
−2cos2(x)
So, the result is: −cos2(x)
Now evaluate the sub-integral.
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The integral of a constant times a function is the constant times the integral of the function:
∫(−2cos(2x))dx=−2∫cos(2x)dx
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Let u=2x.
Then let du=2dx and substitute 2du:
∫4cos(u)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫2cos(u)du=2∫cos(u)du
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The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 2sin(u)
Now substitute u back in:
2sin(2x)
So, the result is: −4sin(2x)
Method #2
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The integral of a constant times a function is the constant times the integral of the function:
∫2xsin(x)cos(x)dx=2∫xsin(x)cos(x)dx
-
Use integration by parts:
∫udv=uv−∫vdu
Let u(x)=x and let dv(x)=sin(x)cos(x).
Then du(x)=1.
To find v(x):
-
Let u=cos(x).
Then let du=−sin(x)dx and substitute −du:
-
The integral of a constant times a function is the constant times the integral of the function:
∫(−u)du=−∫udu
-
The integral of un is n+1un+1 when n=−1:
∫udu=2u2
So, the result is: −2u2
Now substitute u back in:
−2cos2(x)
Now evaluate the sub-integral.
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The integral of a constant times a function is the constant times the integral of the function:
∫(−2cos2(x))dx=−2∫cos2(x)dx
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Rewrite the integrand:
cos2(x)=2cos(2x)+21
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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:
∫2cos(2x)dx=2∫cos(2x)dx
-
Let u=2x.
Then let du=2dx and substitute 2du:
∫4cos(u)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫2cos(u)du=2∫cos(u)du
-
The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 2sin(u)
Now substitute u back in:
2sin(2x)
So, the result is: 4sin(2x)
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The integral of a constant is the constant times the variable of integration:
∫21dx=2x
The result is: 2x+4sin(2x)
So, the result is: −4x−8sin(2x)
So, the result is: −xcos2(x)+2x+4sin(2x)
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Add the constant of integration:
−2xcos(2x)+4sin(2x)+constant
The answer is:
−2xcos(2x)+4sin(2x)+constant
The answer (Indefinite)
[src]
/
| sin(2*x) x*cos(2*x)
| x*sin(2*x) dx = C + -------- - ----------
| 4 2
/
4sin(2x)−2xcos(2x)
The graph
cos(2) sin(2)
- ------ + ------
2 4
4sin2−2cos2
=
cos(2) sin(2)
- ------ + ------
2 4
−2cos(2)+4sin(2)
Use the examples entering the upper and lower limits of integration.