Math Problem Statement

Let f(x) = sin(πx). Use the Mean Value Theorem to find all points 0 < c < 2 such that f(2) - f(0) = f'(c)(2 - 0).

Solution

We are tasked with using the Mean Value Theorem (MVT) to find all points 0<c<20 < c < 2 such that:

f(2)f(0)=f(c)(20)f(2) - f(0) = f'(c)(2 - 0)

where f(x)=sin(πx)f(x) = \sin(\pi x).

Step 1: Apply the Mean Value Theorem

The Mean Value Theorem states that if a function f(x)f(x) is continuous on the closed interval [a,b][a, b] and differentiable on the open interval (a,b)(a, b), then there exists some c(a,b)c \in (a, b) such that:

f(c)=f(b)f(a)baf'(c) = \frac{f(b) - f(a)}{b - a}

In this case:

  • f(x)=sin(πx)f(x) = \sin(\pi x)
  • The interval is [0,2][0, 2]
  • So, a=0a = 0 and b=2b = 2.

Step 2: Calculate f(2)f(2) and f(0)f(0)

We need to calculate f(2)f(2) and f(0)f(0):

  • f(2)=sin(2π)=0f(2) = \sin(2\pi) = 0
  • f(0)=sin(0)=0f(0) = \sin(0) = 0

Thus, the left-hand side of the equation becomes:

f(2)f(0)=00=0f(2) - f(0) = 0 - 0 = 0

Step 3: Differentiate f(x)=sin(πx)f(x) = \sin(\pi x)

Next, we find the derivative of f(x)f(x):

f(x)=ddx[sin(πx)]=πcos(πx)f'(x) = \frac{d}{dx}[\sin(\pi x)] = \pi \cos(\pi x)

Step 4: Set up the equation for cc

Using the Mean Value Theorem, we know there exists c(0,2)c \in (0, 2) such that:

f(c)(20)=f(2)f(0)f'(c)(2 - 0) = f(2) - f(0)

Substitute what we know:

πcos(πc)2=0\pi \cos(\pi c) \cdot 2 = 0

This simplifies to:

πcos(πc)=0\pi \cos(\pi c) = 0

Step 5: Solve for cc

Since π0\pi \neq 0, we must have:

cos(πc)=0\cos(\pi c) = 0

The cosine function equals zero at πc=π2,3π2,\pi c = \frac{\pi}{2}, \frac{3\pi}{2}, \dots. Solving for cc, we find:

c=12,32,c = \frac{1}{2}, \frac{3}{2}, \dots

However, since we are only interested in c(0,2)c \in (0, 2), the only valid solution is:

c=12c = \frac{1}{2}

Conclusion

The point c=12c = \frac{1}{2} satisfies the conditions of the Mean Value Theorem for the given function on the interval (0,2)(0, 2).

Would you like further details or have any questions?

Here are five related questions for deeper understanding:

  1. How does the Mean Value Theorem relate to the concept of differentiability?
  2. Can the Mean Value Theorem be applied to non-differentiable functions?
  3. What is the geometrical interpretation of the Mean Value Theorem?
  4. Why does cos(πc)=0\cos(\pi c) = 0 imply specific values for cc?
  5. How does the result change if we use a different interval, such as [1,3][1, 3]?

Tip: The Mean Value Theorem is a generalization of Rolle's Theorem, which applies when f(a)=f(b)f(a) = f(b).

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Math Problem Analysis

Mathematical Concepts

Calculus
Mean Value Theorem
Trigonometric Functions

Formulas

f'(x) = πcos(πx)
f(b) - f(a) = f'(c)(b - a)
cos(πc) = 0

Theorems

Mean Value Theorem

Suitable Grade Level

Undergraduate (Calculus Level)