微积分I(标准路径) · free preview

§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. The local linearization

The local linearization

2. Suppose that a funct…

Suppose that a function y=f(x)y = f(x) has its tangent line approximation given by L(x)=3−2(x−1)L(x) = 3 - 2(x-1) at the point (1,3)(1,3), but we do not know anything else about the function ff. How can we estimate the value of f(x)f(x) for xx near 11?

3. Estimating with a tangent line

A function gg has tangent line approximation L(x)=−2+3(x+1)L(x) = -2 + 3(x+1) at the point (−1,−2)(-1, -2). What is the best estimate of g(−1.03)g(-1.03)?

4. Building a linearization from data

A function ff satisfies f(2)=−1f(2) = -1 and f′(2)=2f'(2) = 2. Which is its tangent line approximation at 22?

5. Two functions sharing a linearization

Functions ff and gg satisfy f(3)=g(3)=1f(3) = g(3) = 1 and f′(3)=g′(3)=−0.5f'(3) = g'(3) = -0.5. What can be said about their tangent line approximations at 33?

6. Evaluating a linearization

With L(x)=−1+2(x−2)L(x) = -1 + 2(x - 2), estimate f(2.07)f(2.07) by evaluating L(2.07)L(2.07), rounded to two decimals.

7. A second point on the shared line

With the shared linearization L(x)=1−0.5(x−3)L(x) = 1 - 0.5(x - 3), compute L(3.1)L(3.1), rounded to two decimals.

8. Overestimates when the tangent sits above

If the tangent line at x=2x = 2 lies above the graph of ff just to the right of 22, then the estimate f(2.07)≈L(2.07)f(2.07) \approx L(2.07) is too large.

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