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§1.8 The tangent line approximation (continued)

可导函数 $y = f(x)$ 在点 $(a,f(a))$ 处的一般切线近似公式是什么?

1. Exercises (continued)

Exercises (continued)

2. Summary

Summary

3. Curvature and approximation quality

Near x=3x = 3, a shared tangent line LL approximates ff and gg, where f′′(3)=0.2f''(3) = 0.2 and g′′(3)=−1g''(3) = -1. Why does LL approximate ff better?

4. Reading a linearization

A function pp has local linearization L(x)=−2x+5L(x) = -2x + 5 at a=3a = 3. What are p(3)p(3) and p′(3)p'(3)?

5. Estimating with a declining linear model

With local linearization L(x)=−2x+5L(x) = -2x + 5 at a=3a = 3, estimate p(2.79)p(2.79), rounded to two decimals.

6. Concavity decides the error direction

If p′′(x)<0p''(x) \lt 0 for x<3x \lt 3 and LL is the linearization of pp at 33, then L(2.79)L(2.79) overestimates p(2.79)p(2.79).

7. Choosing a central difference

A potato's temperature F(t)F(t) is sampled every 1010 minutes. Which expression best estimates F′(30)F'(30) from the table?

8. A potato temperature forecast

A potato satisfies F(30)=167.6F(30) = 167.6 degrees and F′(30)≈2.065F'(30) \approx 2.065 degrees per minute. Use the tangent line at 3030 to estimate F(33)F(33), rounded to three decimals.

9. Direction of the potato error

The potato's recorded temperatures increase at a decreasing rate near t=30t = 30. Is the tangent line estimate of F(33)F(33) too large or too small?

10. Estimating position from motion data

An object has position s(9)=4s(9) = 4 feet and velocity s′(9)=−1.2s'(9) = -1.2 feet per second at t=9t = 9 seconds. The tangent line estimate of s(9.34)s(9.34) is

11. Direction of the position error

The same object has acceleration s′′(9)=0.08s''(9) = 0.08 feet per second per second. Is the linear estimate s(9.34)≈3.592s(9.34) \approx 3.592 feet too large or too small?

12. Everyday description of the motion

At t=9t = 9 the object is moving toward the origin and slowing down, because its velocity is negative while its acceleration is positive.

13. Zeros of a derivative formula

A function ff has f′(x)=(x−1)e−x2f'(x) = (x-1)e^{-x^2}. At which input is f′(x)=0f'(x) = 0?

14. Concavity from the derivative graph

The graph of f′(x)=(x−1)e−x2f'(x) = (x-1)e^{-x^2} rises on roughly −0.37<x<1.37-0.37 \lt x \lt 1.37 and falls outside that interval. What does this say about ff?

15. A linear estimate for an unknown function

For the same ff with f(2)=−3f(2) = -3, use the tangent line at 22 to estimate f(1.88)f(1.88), given f′(2)=e−4≈0.0183f'(2) = e^{-4} \approx 0.0183. Round to four decimals.

16. Size of the estimate for the unknown function

Near x=2x = 2 the graph of f′(x)=(x−1)e−x2f'(x) = (x-1)e^{-x^2} is decreasing. Is the estimate f(1.88)≈−3.0022f(1.88) \approx -3.0022 too large or too small?

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