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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
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4장, 문제 4.3.53a

Identifying Extrema


In Exercises 53–60:


a. Find the local extrema of each function on the given interval, and say where they occur.


f(x) = sin 2x, 0 ≤ x ≤ π

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To find the local extrema of the function f(x) = sin(2x) on the interval [0, π], we first need to find the critical points. This involves taking the derivative of the function and setting it equal to zero.
The derivative of f(x) = sin(2x) is f'(x) = 2cos(2x). Set this equal to zero to find the critical points: 2cos(2x) = 0.
Solve the equation cos(2x) = 0. The solutions to this equation are 2x = π/2 + kπ, where k is an integer. Divide by 2 to solve for x: x = π/4 + kπ/2.
Determine which of these critical points lie within the interval [0, π]. For k = 0, x = π/4; for k = 1, x = 3π/4. Both are within the interval.
Evaluate the function f(x) at the critical points and the endpoints of the interval, x = 0 and x = π, to determine the local extrema. Compare these values to identify the local maxima and minima.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Local Extrema

Local extrema refer to the points in a function where it reaches a local maximum or minimum value. These points occur where the derivative of the function is zero or undefined, indicating a change in the direction of the function's slope. Identifying local extrema involves finding these critical points and evaluating the function's behavior around them.
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05:58
Finding Extrema Graphically

Derivative and Critical Points

The derivative of a function provides the rate of change or slope of the function at any given point. Critical points occur where the derivative is zero or undefined, which are potential locations for local extrema. To find these points, differentiate the function and solve for the values of x that satisfy these conditions within the given interval.
추천 영상:
04:50
Critical Points

Trigonometric Functions and Their Derivatives

Understanding the behavior of trigonometric functions like sine is crucial for solving problems involving them. The derivative of sin(2x) is 2cos(2x), which helps in finding critical points. Analyzing the sine and cosine functions over the interval [0, π] allows us to determine where the function increases or decreases, aiding in identifying local extrema.
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가이드 코스
6:04
Introduction to Trigonometric Functions