Math Problem Statement

Verify Rolle's theorem for f (x)=sinx+2 for 0=<x=<2π

Solution

To verify Rolle's Theorem for f(x)=sin(x)+2f(x) = \sin(x) + 2 on the interval [0,2π][0, 2\pi], we need to ensure that the function satisfies the three conditions of Rolle's Theorem:

Rolle's Theorem Conditions:

  1. The function must be continuous on the closed interval [a,b][a, b].
  2. The function must be differentiable on the open interval (a,b)(a, b).
  3. The function values at the endpoints must be equal, i.e., f(a)=f(b)f(a) = f(b).

Step 1: Continuity and Differentiability

  • The function f(x)=sin(x)+2f(x) = \sin(x) + 2 is continuous and differentiable everywhere, including on the interval [0,2π][0, 2\pi], because sine is continuous and differentiable, and adding a constant does not affect continuity or differentiability.

Thus, the first two conditions are satisfied.

Step 2: Checking f(a)=f(b)f(a) = f(b)

We now check the values of the function at the endpoints x=0x = 0 and x=2πx = 2\pi.

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

Since f(0)=f(2π)f(0) = f(2\pi), the third condition is satisfied.

Step 3: Finding c(0,2π)c \in (0, 2\pi) such that f(c)=0f'(c) = 0

Now, we need to find a point c(0,2π)c \in (0, 2\pi) where the derivative of f(x)f(x) equals zero.

  • First, compute the derivative of f(x)f(x): f(x)=cos(x)f'(x) = \cos(x)

  • Now, solve for xx such that f(x)=0f'(x) = 0: cos(x)=0\cos(x) = 0 The cosine function equals zero at: x=π2,3π2x = \frac{\pi}{2}, \frac{3\pi}{2}

Both π2\frac{\pi}{2} and 3π2\frac{3\pi}{2} lie within the open interval (0,2π)(0, 2\pi).

Conclusion:

Rolle's Theorem is satisfied for f(x)=sin(x)+2f(x) = \sin(x) + 2 on the interval [0,2π][0, 2\pi], with points c=π2c = \frac{\pi}{2} and c=3π2c = \frac{3\pi}{2} where f(c)=0f'(c) = 0.


Would you like further clarification on any step? Here are five related questions to expand your understanding:

  1. How does Rolle's Theorem apply to non-trigonometric functions?
  2. What happens if the function isn't differentiable at some point within the interval?
  3. How can we interpret the geometric meaning of Rolle's Theorem?
  4. Can a function have more than one value of cc that satisfies Rolle's Theorem?
  5. How does Rolle’s Theorem relate to the Mean Value Theorem?

Tip: When solving Rolle’s Theorem problems, always verify continuity, differentiability, and endpoint equality before finding where the derivative is zero.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Trigonometry

Formulas

Derivative of sin(x)
f'(x) = cos(x)

Theorems

Rolle's Theorem

Suitable Grade Level

Grades 11-12 or College Level Calculus