Math Problem Statement

graph the function over -2pi less than or equal to x 2pi greater than or equal to x using technology. use the graph to estimate the value of lim(gx) as x approaches 0. then justify answer using algebra

(4x+x^3sin(2pix+pi))/(6x)

Solution

The graph of the function g(x)=4x+x3sin(2πx+π)6xg(x) = \frac{4x + x^3 \sin(2\pi x + \pi)}{6x} over the interval [2π,2π][-2\pi, 2\pi] is shown above.

Step 2: Estimate the Limit from the Graph

From the graph, as xx approaches 0, the value of g(x)g(x) appears to approach 23\frac{2}{3}.

Step 3: Justify the Limit Algebraically

To find the limit algebraically, we calculate:

limx0g(x)=limx04x+x3sin(2πx+π)6x\lim_{x \to 0} g(x) = \lim_{x \to 0} \frac{4x + x^3 \sin(2\pi x + \pi)}{6x}

We can separate the limit into two parts:

limx0g(x)=limx0(4x6x+x3sin(2πx+π)6x)\lim_{x \to 0} g(x) = \lim_{x \to 0} \left(\frac{4x}{6x} + \frac{x^3 \sin(2\pi x + \pi)}{6x}\right)

Simplifying each term:

limx04x6x=46=23\lim_{x \to 0} \frac{4x}{6x} = \frac{4}{6} = \frac{2}{3}

For the second term:

limx0x3sin(2πx+π)6x=limx0x2sin(2πx+π)6\lim_{x \to 0} \frac{x^3 \sin(2\pi x + \pi)}{6x} = \lim_{x \to 0} \frac{x^2 \sin(2\pi x + \pi)}{6}

As x0x \to 0, sin(2πx+π)\sin(2\pi x + \pi) is bounded, so x2sin(2πx+π)x^2 \sin(2\pi x + \pi) approaches 0. Therefore:

limx0x2sin(2πx+π)6=0\lim_{x \to 0} \frac{x^2 \sin(2\pi x + \pi)}{6} = 0

Thus, the overall limit is:

limx0g(x)=23+0=23\lim_{x \to 0} g(x) = \frac{2}{3} + 0 = \frac{2}{3}

This confirms the estimate from the graph.

Would you like more details or have any questions?

Here are 5 related questions:

  1. How do limits behave when dealing with trigonometric functions?
  2. What is L'Hôpital's Rule, and when can it be used for limits?
  3. How do you determine the continuity of a function at a point?
  4. What role does the squeeze theorem play in evaluating limits?
  5. How can you verify a limit algebraically when the function involves polynomials and trigonometric terms?

Tip: When estimating limits from a graph, always check for continuity and smooth behavior around the point of interest to ensure accuracy.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometric Functions
Algebra

Formulas

Limit definition
Squeeze theorem

Theorems

Limit properties

Suitable Grade Level

Advanced High School