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The derivative of the function 
f is defined by 
f^(')(x)=(x^(3)-5x)cos(2x). If 
f(-1)=-4, then use a calculator to find the value of 
f(6) to the nearest thousandth.
Answer:

The derivative of the function f f is defined by f(x)=(x35x)cos(2x) f^{\prime}(x)=\left(x^{3}-5 x\right) \cos (2 x) . If f(1)=4 f(-1)=-4 , then use a calculator to find the value of f(6) f(6) to the nearest thousandth.\newlineAnswer:

Full solution

Q. The derivative of the function f f is defined by f(x)=(x35x)cos(2x) f^{\prime}(x)=\left(x^{3}-5 x\right) \cos (2 x) . If f(1)=4 f(-1)=-4 , then use a calculator to find the value of f(6) f(6) to the nearest thousandth.\newlineAnswer:
  1. Integrate f(x)f'(x): To find f(6)f(6), we need to integrate f(x)f'(x) from 1-1 to 66 and add the result to f(1)f(-1).
  2. Apply integration by parts: The integral of f(x)f'(x) is (x35x)cos(2x)dx\int(x^{3}-5x)\cos(2x) \, dx. We will use integration by parts and trigonometric identities to solve this.
  3. Integrate (12)sin(2x)(3x25)dx(\frac{1}{2})\sin(2x)(3x^{2}-5) dx: Let u=x35xu = x^{3}-5x, then du=(3x25)dxdu = (3x^{2}-5) dx. Let dv=cos(2x)dxdv = \cos(2x) dx, then v=(12)sin(2x)v = (\frac{1}{2})\sin(2x) using the integral of cosine.
  4. Apply integration by parts again: Using integration by parts, udv=uvvdu\int u\,dv = uv - \int v\,du. We apply this to our integral: (x35x)cos(2x)dx=12x3sin(2x)12sin(2x)(3x25)dx\int(x^{3}-5x)\cos(2x) \,dx = \frac{1}{2}x^{3}\sin(2x) - \int\frac{1}{2}\sin(2x)(3x^{2}-5) \,dx.
  5. Integrate 32xcos(2x)dx-\frac{3}{2}x \cos(2x) \,dx: We now need to integrate 12sin(2x)(3x25)dx\int \frac{1}{2}\sin(2x)(3x^{2}-5) \,dx. This requires another integration by parts.
  6. Combine all parts of the integral: Let u=(3x25)u = (3x^{2}-5), then du=6xdxdu = 6x \, dx. Let dv=(12)sin(2x)dxdv = (\frac{1}{2})\sin(2x) \, dx, then v=(14)cos(2x)v = -(\frac{1}{4})\cos(2x) using the integral of sine.
  7. Evaluate the definite integral: Applying integration by parts again, we get (12)sin(2x)(3x25)dx=(14)(3x25)cos(2x)(14)cos(2x)(6x)dx\int (\frac{1}{2})\sin(2x)(3x^{2}-5) \, dx = -(\frac{1}{4})(3x^{2}-5)\cos(2x) - \int -(\frac{1}{4})\cos(2x)(6x) \, dx.
  8. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.
  9. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).
  10. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx.
  11. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts. Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x). Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx. The remaining integral is (14)(3)sin(2x)dx\int(\frac{1}{4})(-3)\sin(2x) \, dx, which simplifies to (34)sin(2x)dx-(\frac{3}{4}) \int\sin(2x) \, dx. The integral of (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx00 is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx11.
  12. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx.The remaining integral is (14)(3)sin(2x)dx\int(\frac{1}{4})(-3)\sin(2x) \, dx, which simplifies to (34)sin(2x)dx-(\frac{3}{4}) \int\sin(2x) \, dx. The integral of (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx00 is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx11.So, (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx22. Now we combine all parts of the integral we've calculated.
  13. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int -(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx.The remaining integral is (14)(3)sin(2x)dx\int(\frac{1}{4})(-3)\sin(2x) \, dx, which simplifies to (34)sin(2x)dx-(\frac{3}{4}) \int\sin(2x) \, dx. The integral of (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx00 is (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx11.So, (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx22. Now we combine all parts of the integral we've calculated.The integral from (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx33 to (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx44 of (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx55 is the sum of all the parts we've integrated by parts. We need to evaluate this definite integral and add it to (14)cos(2x)(6x)dx\int -(\frac{1}{4})\cos(2x)(6x) \, dx66.
  14. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx.The remaining integral is (14)(3)sin(2x)dx\int(\frac{1}{4})(-3)\sin(2x) \, dx, which simplifies to (34)sin(2x)dx-(\frac{3}{4}) \int\sin(2x) \, dx. The integral of (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx00 is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx11.So, (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx22. Now we combine all parts of the integral we've calculated.The integral from (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx33 to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx44 of (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx55 is the sum of all the parts we've integrated by parts. We need to evaluate this definite integral and add it to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx66.We evaluate the integral at the bounds (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx44 and (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx33, subtract the lower bound evaluation from the upper bound evaluation, and add the result to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx66.
  15. Calculate f(6)f(6): The remaining integral is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx, which simplifies to (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx. This requires another integration by parts.Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(12)cos(2x)dxdv = (\frac{1}{2})\cos(2x) \, dx, then v=(14)sin(2x)v = (\frac{1}{4})\sin(2x).Applying integration by parts, we get (32)xcos(2x)dx=(14)(3x)sin(2x)(14)(3)sin(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx = (\frac{1}{4})(-3x)\sin(2x) - \int(\frac{1}{4})(-3)\sin(2x) \, dx.The remaining integral is (14)(3)sin(2x)dx\int(\frac{1}{4})(-3)\sin(2x) \, dx, which simplifies to (34)sin(2x)dx-(\frac{3}{4}) \int\sin(2x) \, dx. The integral of (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx00 is (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx11.So, (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx22. Now we combine all parts of the integral we've calculated.The integral from (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx33 to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx44 of (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx55 is the sum of all the parts we've integrated by parts. We need to evaluate this definite integral and add it to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx66.We evaluate the integral at the bounds (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx44 and (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx33, subtract the lower bound evaluation from the upper bound evaluation, and add the result to (14)cos(2x)(6x)dx\int-(\frac{1}{4})\cos(2x)(6x) \, dx66.Using a calculator to evaluate the integral at (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx00 and (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx11, we find the change in (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx22 over this interval. We then add this change to (32)xcos(2x)dx\int-(\frac{3}{2})x \cos(2x) \, dx33 to find f(6)f(6).
  16. Calculate f(6)f(6): The remaining integral is (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx, which simplifies to (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx. This requires another integration by parts. Let u=3xu = -3x, then du=3dxdu = -3 \, dx. Let dv=(1/2)cos(2x)dxdv = (1/2)\cos(2x) \, dx, then v=(1/4)sin(2x)v = (1/4)\sin(2x). Applying integration by parts, we get (3/2)xcos(2x)dx=(1/4)(3x)sin(2x)(1/4)(3)sin(2x)dx\int -(3/2)x \cos(2x) \, dx = (1/4)(-3x)\sin(2x) - \int (1/4)(-3)\sin(2x) \, dx. The remaining integral is (1/4)(3)sin(2x)dx\int (1/4)(-3)\sin(2x) \, dx, which simplifies to (3/4)sin(2x)dx-(3/4) \int \sin(2x) \, dx. The integral of (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx00 is (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx11. So, (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx22. Now we combine all parts of the integral we've calculated. The integral from (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx33 to (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx44 of (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx55 is the sum of all the parts we've integrated by parts. We need to evaluate this definite integral and add it to (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx66. We evaluate the integral at the bounds (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx44 and (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx33, subtract the lower bound evaluation from the upper bound evaluation, and add the result to (1/4)cos(2x)(6x)dx\int -(1/4)\cos(2x)(6x) \, dx66. Using a calculator to evaluate the integral at (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx00 and (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx11, we find the change in (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx22 over this interval. We then add this change to (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx33 to find f(6)f(6). After calculating the definite integral and adding it to (3/2)xcos(2x)dx\int -(3/2)x \cos(2x) \, dx33, we round the result to the nearest thousandth to get the final answer.

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