Integral of x*cos(x/2) dx
The solution
Detail solution
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Use integration by parts:
∫udv=uv−∫vdu
Let u(x)=x and let dv(x)=cos(2x).
Then du(x)=1.
To find v(x):
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Let u=2x.
Then let du=2dx and substitute 2du:
∫2cos(u)du
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The integral of a constant times a function is the constant times the integral of the function:
∫cos(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)
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:
∫2sin(2x)dx=2∫sin(2x)dx
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Let u=2x.
Then let du=2dx and substitute 2du:
∫2sin(u)du
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The integral of a constant times a function is the constant times the integral of the function:
∫sin(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)
So, the result is: −4cos(2x)
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Add the constant of integration:
2xsin(2x)+4cos(2x)+constant
The answer is:
2xsin(2x)+4cos(2x)+constant
The answer (Indefinite)
[src]
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| /x\ /x\ /x\
| x*cos|-| dx = C + 4*cos|-| + 2*x*sin|-|
| \2/ \2/ \2/
|
/
∫xcos(2x)dx=C+2xsin(2x)+4cos(2x)
The graph
-4 + 2*sin(1/2) + 4*cos(1/2)
−4+2sin(21)+4cos(21)
=
-4 + 2*sin(1/2) + 4*cos(1/2)
−4+2sin(21)+4cos(21)
-4 + 2*sin(1/2) + 4*cos(1/2)
Use the examples entering the upper and lower limits of integration.