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Ch. 3 - Derivatives
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 3, Problem 3.8.65b

Vertical tangent lines
b. Does the curve have any horizontal tangent lines? Explain.

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1
To determine if the curve has any horizontal tangent lines, we need to find the derivative of the function that defines the curve. The derivative will give us the slope of the tangent line at any point on the curve.
Set the derivative equal to zero and solve for the variable. This is because a horizontal tangent line has a slope of zero.
Identify the points on the curve where the derivative is zero. These points are where the curve may have horizontal tangent lines.
Verify if these points are indeed on the curve by substituting them back into the original equation of the curve.
Discuss the behavior of the curve at these points to confirm if they correspond to horizontal tangent lines, considering the context of the problem and any constraints given.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Tangent Lines

Tangent lines are straight lines that touch a curve at a single point without crossing it. The slope of the tangent line at a point on the curve represents the instantaneous rate of change of the function at that point. Understanding tangent lines is crucial for analyzing the behavior of curves, particularly in determining where they are increasing or decreasing.
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Vertical Tangent Lines

A vertical tangent line occurs when the slope of the tangent approaches infinity, which typically happens when the derivative of the function is undefined at that point. This indicates that the curve is steeply increasing or decreasing, and it can signify a cusp or a vertical asymptote. Identifying vertical tangents helps in understanding the nature of the curve's behavior at specific points.
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Slopes of Tangent Lines

Horizontal Tangent Lines

A horizontal tangent line occurs when the slope of the tangent line is zero, indicating that the function has a local maximum or minimum at that point. This means that the rate of change of the function is momentarily flat, and it is essential for finding critical points in optimization problems. Analyzing horizontal tangents is key to understanding the overall shape and turning points of a curve.
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Slopes of Tangent Lines