The derivative of the function f is defined by f′(x)=x2−4x+2cos(2x−4). If f(0)=1, then use a calculator to find the value of f(6) to the nearest thousandth.Answer:
Q. The derivative of the function f is defined by f′(x)=x2−4x+2cos(2x−4). If f(0)=1, then use a calculator to find the value of f(6) to the nearest thousandth.Answer:
Set up integral: To find the value of f(6), we need to integrate the derivative f′(x) from 0 to 6 and then add the initial value f(0) to the result of the integration.
Integrate each term: First, we set up the integral of f′(x) from 0 to 6:∫06(x2−4x+2cos(2x−4))dx
Evaluate integrals: We integrate each term separately:∫06x2dx=[3x3]06∫06−4xdx=[−2x2]06∫062cos(2x−4)dx=[sin(2x−4)]06 (Note: We need to use substitution for this integral)
Substitute and integrate: We evaluate each integral at the bounds 0 and 6: [3x3] (from 0 to 6) = (363)−(303) = 72 [−2x2] (from 0 to 6) = 60 = 61 For the cosine integral, we use substitution: let 62, then 63, so 64.
Evaluate cosine integral: Now we integrate 2cos(u) with respect to u: ∫2cos(u)du=2sin(u) We need to change the limits of integration according to the substitution: When x=0, u=2⋅0−4=−4 When x=6, u=2⋅6−4=8 So we evaluate 2sin(u) from u=−4 to u=8.
Add integrals: We find the value of the integral of the cosine term:2sin(u) (from u=−4 to u=8) = 2sin(8)−2sin(−4)Using a calculator, we find:2sin(8)≈2×0.989=1.9782sin(−4)≈2×(−0.756)=−1.512So the integral from −4 to 8 is approximately 1.978−(−1.512)=3.490
Add initial value: We add the results of the integrals: 72−72+3.490=3.490
Add initial value: We add the results of the integrals: 72−72+3.490=3.490 Finally, we add the initial value f(0)=1 to the result of the integration to find f(6): f(6)=1+3.490=4.490
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