The Mean Value Theorem — Question 10

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Question 10

Problem:

Let f(x)=sin⁡(x)f(x) = \sin(x) on the interval [0,π]\left[0, \pi\right].

  • (a) Verify that f(x)f(x) satisfies the conditions of the Mean Value Theorem on [0,π]\left[0, \pi\right].

  • (b) Find all values of c∈(0,π)c \in (0, \pi) such that f′(c)=f(π)−f(0)π−0.f'(c) = \frac{f(\pi) - f(0)}{\pi - 0}.

Original worksheet page 1: question and worked solution for 4-7-010
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Question 10 - Solution

We are given: f(x)=sin⁡(x)f(x) = \sin(x)

(a) Conditions for MVT:

- f(x)f(x) is continuous on [0,π][0, \pi] ✓ - f(x)f(x) is differentiable on (0,π)(0, \pi) ✓

✅ MVT applies.

(b) Apply MVT:

f(π)=0,f(0)=0f(\pi) = 0, \quad f(0) = 0 f(π)−f(0)π−0=0−0π=0\frac{f(\pi) - f(0)}{\pi - 0} = \frac{0 - 0}{\pi} = 0

We need: f′(c)=cos⁡(c)=0⇒c=π2f'(c) = \cos(c) = 0 \Rightarrow c = \frac{\pi}{2}

c=π2\boxed{c = \frac{\pi}{2}}

Graph of f(x)=sin⁡(x)f(x) = \sin(x) on [0,π][0, \pi]:

See the diagram in the original worksheet below.

Original worksheet page 2: question and worked solution for 4-7-010

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