Math Problem Statement

Use the graphing guidelines to make a complete graph of f(x) = 3e^{-x} sin(x) on [-π, π].

Solution

To create a complete graph of the function f(x)=3exsin(x)f(x) = 3e^{-x} \sin(x) over the interval [π,π][-\pi, \pi], let's follow these graphing guidelines:

Step 1: Identify Key Characteristics

  1. Domain: The function f(x)=3exsin(x)f(x) = 3e^{-x} \sin(x) is defined on the entire real line, but we are only interested in x[π,π]x \in [-\pi, \pi].
  2. Range: Since exe^{-x} is always positive and sin(x)\sin(x) oscillates between -1 and 1, the range will depend on this oscillation and the exponential decay/growth.
  3. Symmetry: The function is neither even nor odd, so it lacks symmetry around the origin or the y-axis.
  4. Asymptotes: There are no vertical or horizontal asymptotes within this interval, though exe^{-x} generally trends towards zero as xx increases for large values beyond this interval.
  5. Behavior at Critical Points: We'll identify critical points by finding the derivative of f(x)f(x) and setting it to zero.

Step 2: First Derivative and Critical Points

To find the critical points, calculate f(x)f'(x) using the product rule.

  1. f(x)=3exsin(x)f(x) = 3e^{-x} \sin(x)
  2. Using the product rule, f(x)=3(exsin(x)+excos(x))=3ex(sin(x)+cos(x))f'(x) = 3 \left( -e^{-x} \sin(x) + e^{-x} \cos(x) \right) = 3e^{-x}(-\sin(x) + \cos(x)).

Set f(x)=0f'(x) = 0: 3ex(sin(x)+cos(x))=0.3e^{-x}(-\sin(x) + \cos(x)) = 0. Since ex0e^{-x} \neq 0 for real xx, we get sin(x)+cos(x)=0-\sin(x) + \cos(x) = 0 or tan(x)=1\tan(x) = 1.

Step 3: Solving for xx

Within x[π,π]x \in [-\pi, \pi], the solutions to tan(x)=1\tan(x) = 1 are:

  1. x=π4x = \frac{\pi}{4}
  2. x=3π4x = -\frac{3\pi}{4}.

Step 4: Second Derivative and Concavity

For concavity analysis, calculate the second derivative f(x)f''(x) and determine where it changes sign. This will indicate intervals of concave up or down, aiding in understanding the curve’s behavior.

Step 5: Plotting the Graph

  • Plot points at key locations: Evaluate f(x)f(x) at x=π,3π4,0,π4,πx = -\pi, -\frac{3\pi}{4}, 0, \frac{\pi}{4}, \pi.
  • Determine concavity: Use the second derivative to establish concave up/down intervals.
  • Sketch the function: The graph should oscillate due to sin(x)\sin(x), with amplitudes modulated by exe^{-x}.

Would you like a plotted graph for this function, or further analysis on any of these steps?


Here are five related questions for deeper understanding:

  1. How does the behavior of exe^{-x} affect the oscillation of sin(x)\sin(x) in this graph?
  2. What would happen to the graph if the interval were larger, say [2π,2π][-2\pi, 2\pi]?
  3. How do critical points help in determining the shape of the graph?
  4. Can we identify local maximums or minimums on this interval for this function?
  5. How would the graph change if the coefficient 3 were different, say 1 or 5?

Tip: When graphing, analyzing the first and second derivatives can significantly clarify where a function increases, decreases, or changes concavity, helping in sketching the graph accurately.

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Math Problem Analysis

Mathematical Concepts

Calculus
Graphing functions
Exponential functions
Trigonometric functions

Formulas

f(x) = 3e^{-x}sin(x)
Product rule for derivatives
First and second derivative

Theorems

First Derivative Test
Second Derivative Test

Suitable Grade Level

Grades 11-12 or introductory college level