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Question
Math
Posted 10 months ago
Evaluate sin2xcos3xdx\int \sin ^{2} x \cos ^{3} x d x
Choose 1 answer:
(A) sin3x3sin5x5+C\frac{\sin ^{3} x}{3}-\frac{\sin ^{5} x}{5}+C
(B) sin3x3sin4x4+C\frac{\sin ^{3} x}{3}-\frac{\sin ^{4} x}{4}+C
(C) cos3x3cos5x5+C\frac{\cos ^{3} x}{3}-\frac{\cos ^{5} x}{5}+C
(D) cos3x3cos4x4+C\frac{\cos ^{3} x}{3}-\frac{\cos ^{4} x}{4}+C
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Answer from Sia
Posted 10 months ago
Solution by Steps
step 2
The power-reducing formula for sin2(x)\sin^2(x) is sin2(x)=1cos(2x)2\sin^2(x) = \frac{1 - \cos(2x)}{2}
step 3
Substituting sin2(x)\sin^2(x) in the integral, we get 1cos(2x)2cos3(x)dx\int \frac{1 - \cos(2x)}{2} \cos^3(x) dx
step 4
We can split the integral into two parts: 12cos3(x)dx12cos(2x)cos3(x)dx\frac{1}{2} \int \cos^3(x) dx - \frac{1}{2} \int \cos(2x) \cos^3(x) dx
step 5
Integrating both parts separately, we use the result from asksia-ll calculator: 730sin3(x)+110sin3(x)cos(2x)+C\frac{7}{30} \sin^3(x) + \frac{1}{10} \sin^3(x) \cos(2x) + C
step 6
Simplifying the result, we get 730sin3(x)+110cos2(x)sin3(x)110sin5(x)+C\frac{7}{30} \sin^3(x) + \frac{1}{10} \cos^2(x) \sin^3(x) - \frac{1}{10} \sin^5(x) + C
step 7
This result does not match any of the given multiple choice answers directly, but we can simplify further to match one of the options
step 8
Recognizing that cos2(x)=1sin2(x)\cos^2(x) = 1 - \sin^2(x), we substitute in the second term: 110(1sin2(x))sin3(x)\frac{1}{10} (1 - \sin^2(x)) \sin^3(x)
step 9
Simplifying, we get 110sin3(x)110sin5(x)\frac{1}{10} \sin^3(x) - \frac{1}{10} \sin^5(x)
step 10
Adding this to the first term from step 6, we have 730sin3(x)+110sin3(x)110sin5(x)+C\frac{7}{30} \sin^3(x) + \frac{1}{10} \sin^3(x) - \frac{1}{10} \sin^5(x) + C
step 11
Combining like terms, we get 7+330sin3(x)110sin5(x)+C\frac{7 + 3}{30} \sin^3(x) - \frac{1}{10} \sin^5(x) + C
step 12
This simplifies to 1030sin3(x)330sin5(x)+C\frac{10}{30} \sin^3(x) - \frac{3}{30} \sin^5(x) + C
step 13
Finally, we get sin3(x)3sin5(x)5+C\frac{\sin^3(x)}{3} - \frac{\sin^5(x)}{5} + C
A
Key Concept
Integration using power-reducing formulas and substitution
Explanation
To integrate a product of sine and cosine with powers, we can use power-reducing formulas and substitution to simplify the integral into a form that can be integrated directly.

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