Integral of cos^2(3x)sin^4(3x) dx
The solution
Detail solution
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Rewrite the integrand:
sin4(3x)cos2(3x)=(21−2cos(6x))2(2cos(6x)+21)
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There are multiple ways to do this integral.
Method #1
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Let u=6x.
Then let du=6dx and substitute du:
∫(48cos3(u)−48cos2(u)−48cos(u)+481)du
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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:
∫48cos3(u)du=48∫cos3(u)du
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Rewrite the integrand:
cos3(u)=(1−sin2(u))cos(u)
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Let u=sin(u).
Then let du=cos(u)du and substitute du:
∫(1−u2)du
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Integrate term-by-term:
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The integral of a constant is the constant times the variable of integration:
∫1du=u
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The integral of a constant times a function is the constant times the integral of the function:
∫(−u2)du=−∫u2du
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The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
So, the result is: −3u3
The result is: −3u3+u
Now substitute u back in:
−3sin3(u)+sin(u)
So, the result is: −144sin3(u)+48sin(u)
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The integral of a constant times a function is the constant times the integral of the function:
∫(−48cos2(u))du=−48∫cos2(u)du
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Rewrite the integrand:
cos2(u)=2cos(2u)+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(2u)du=2∫cos(2u)du
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Let u=2u.
Then let du=2du 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(2u)
So, the result is: 4sin(2u)
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The integral of a constant is the constant times the variable of integration:
∫21du=2u
The result is: 2u+4sin(2u)
So, the result is: −96u−192sin(2u)
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The integral of a constant times a function is the constant times the integral of the function:
∫(−48cos(u))du=−48∫cos(u)du
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The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: −48sin(u)
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The integral of a constant is the constant times the variable of integration:
∫481du=48u
The result is: 96u−192sin(2u)−144sin3(u)
Now substitute u back in:
16x−144sin3(6x)−192sin(12x)
Method #2
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Rewrite the integrand:
(21−2cos(6x))2(2cos(6x)+21)=8cos3(6x)−8cos2(6x)−8cos(6x)+81
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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:
∫8cos3(6x)dx=8∫cos3(6x)dx
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Rewrite the integrand:
cos3(6x)=(1−sin2(6x))cos(6x)
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Let u=sin(6x).
Then let du=6cos(6x)dx and substitute du:
∫(61−6u2)du
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Integrate term-by-term:
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The integral of a constant is the constant times the variable of integration:
∫61du=6u
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The integral of a constant times a function is the constant times the integral of the function:
∫(−6u2)du=−6∫u2du
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The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
So, the result is: −18u3
The result is: −18u3+6u
Now substitute u back in:
−18sin3(6x)+6sin(6x)
So, the result is: −144sin3(6x)+48sin(6x)
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The integral of a constant times a function is the constant times the integral of the function:
∫(−8cos2(6x))dx=−8∫cos2(6x)dx
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Rewrite the integrand:
cos2(6x)=2cos(12x)+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(12x)dx=2∫cos(12x)dx
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Let u=12x.
Then let du=12dx and substitute 12du:
∫12cos(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=12∫cos(u)du
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The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 12sin(u)
Now substitute u back in:
12sin(12x)
So, the result is: 24sin(12x)
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The integral of a constant is the constant times the variable of integration:
∫21dx=2x
The result is: 2x+24sin(12x)
So, the result is: −16x−192sin(12x)
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The integral of a constant times a function is the constant times the integral of the function:
∫(−8cos(6x))dx=−8∫cos(6x)dx
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Let u=6x.
Then let du=6dx and substitute 6du:
∫6cos(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=6∫cos(u)du
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The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 6sin(u)
Now substitute u back in:
6sin(6x)
So, the result is: −48sin(6x)
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The integral of a constant is the constant times the variable of integration:
∫81dx=8x
The result is: 16x−144sin3(6x)−192sin(12x)
Method #3
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Rewrite the integrand:
(21−2cos(6x))2(2cos(6x)+21)=8cos3(6x)−8cos2(6x)−8cos(6x)+81
-
Integrate term-by-term:
-
The integral of a constant times a function is the constant times the integral of the function:
∫8cos3(6x)dx=8∫cos3(6x)dx
-
Rewrite the integrand:
cos3(6x)=(1−sin2(6x))cos(6x)
-
Let u=sin(6x).
Then let du=6cos(6x)dx and substitute du:
∫(61−6u2)du
-
Integrate term-by-term:
-
The integral of a constant is the constant times the variable of integration:
∫61du=6u
-
The integral of a constant times a function is the constant times the integral of the function:
∫(−6u2)du=−6∫u2du
-
The integral of un is n+1un+1 when n=−1:
∫u2du=3u3
So, the result is: −18u3
The result is: −18u3+6u
Now substitute u back in:
−18sin3(6x)+6sin(6x)
So, the result is: −144sin3(6x)+48sin(6x)
-
The integral of a constant times a function is the constant times the integral of the function:
∫(−8cos2(6x))dx=−8∫cos2(6x)dx
-
Rewrite the integrand:
cos2(6x)=2cos(12x)+21
-
Integrate term-by-term:
-
The integral of a constant times a function is the constant times the integral of the function:
∫2cos(12x)dx=2∫cos(12x)dx
-
Let u=12x.
Then let du=12dx and substitute 12du:
∫12cos(u)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫cos(u)du=12∫cos(u)du
-
The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 12sin(u)
Now substitute u back in:
12sin(12x)
So, the result is: 24sin(12x)
-
The integral of a constant is the constant times the variable of integration:
∫21dx=2x
The result is: 2x+24sin(12x)
So, the result is: −16x−192sin(12x)
-
The integral of a constant times a function is the constant times the integral of the function:
∫(−8cos(6x))dx=−8∫cos(6x)dx
-
Let u=6x.
Then let du=6dx and substitute 6du:
∫6cos(u)du
-
The integral of a constant times a function is the constant times the integral of the function:
∫cos(u)du=6∫cos(u)du
-
The integral of cosine is sine:
∫cos(u)du=sin(u)
So, the result is: 6sin(u)
Now substitute u back in:
6sin(6x)
So, the result is: −48sin(6x)
-
The integral of a constant is the constant times the variable of integration:
∫81dx=8x
The result is: 16x−144sin3(6x)−192sin(12x)
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Add the constant of integration:
16x−144sin3(6x)−192sin(12x)+constant
The answer is:
16x−144sin3(6x)−192sin(12x)+constant
The answer (Indefinite)
[src]
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| 3
| 2 4 sin (6*x) sin(12*x) x
| cos (3*x)*sin (3*x) dx = C - --------- - --------- + --
| 144 192 16
/
∫sin4(3x)cos2(3x)dx=C+16x−144sin3(6x)−192sin(12x)
The graph
Use the examples entering the upper and lower limits of integration.