Identify Integral: Identify the integral to be solved.We need to evaluate the integral of 4x3sin(4x) with respect to x, which is written as ∫4x3sin(4x)dx.
Use Integration by Parts: Use integration by parts. Integration by parts is given by the formula ∫udv=uv−∫vdu, where u and dv are parts of the integrand. We need to choose u and dv such that the resulting integral is simpler. Let's choose u=x3 (which will simplify when differentiated) and dv=4sin(4x)dx (which will integrate easily).
Differentiate and Integrate: Differentiate u and integrate dv.Differentiating u=x3 gives us du=3x2dx.Integrating dv=4sin(4x)dx gives us v=−cos(4x).
Apply Integration by Parts: Apply the integration by parts formula.Now we apply the integration by parts formula:∫4x3sin(4x)dx=uv−∫vdu=x3(−cos(4x))−∫(−cos(4x))(3x2)dx=−x3cos(4x)+3∫x2cos(4x)dx
Apply Integration by Parts Again: Apply integration by parts again to the remaining integral.We need to apply integration by parts to the integral 3∫x2cos(4x)dx. Let's choose u=x2 and dv=3cos(4x)dx.Differentiating u=x2 gives us du=2xdx.Integrating dv=3cos(4x)dx gives us v=43sin(4x).
Apply Integration by Parts Formula: Apply the integration by parts formula to the new integral.Now we apply the integration by parts formula to the new integral:3∫x2cos(4x)dx=uv−∫vdu=x2(43)sin(4x)−∫(43)sin(4x)(2x)dx=(43)x2sin(4x)−(23)∫xsin(4x)dx
Apply Integration by Parts One More Time: Apply integration by parts one more time to the remaining integral.We need to apply integration by parts to the integral (23)∫xsin(4x)dx. Let's choose u=x and dv=(23)sin(4x)dx.Differentiating u=x gives us du=dx.Integrating dv=(23)sin(4x)dx gives us v=−(83)cos(4x).
Apply Integration by Parts Formula: Apply the integration by parts formula to the final integral.Now we apply the integration by parts formula to the final integral:(23)∫xsin(4x)dx=uv−∫vdu=x(−83)cos(4x)−∫(−83)cos(4x)dx=−(83)xcos(4x)+(83)(41)sin(4x)=−(83)xcos(4x)+(323)sin(4x)
Combine All Parts: Combine all parts to get the final answer.Combining all parts, we get:∫4x3sin(4x)dx=−x3cos(4x)+43x2sin(4x)−83xcos(4x)+323sin(4x)+Cwhere C is the constant of integration.
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