/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 74 \(71-74\). Find all solutions of... [FREE SOLUTION] | 91Ó°ÊÓ

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\(71-74\). Find all solutions of the equation that lie in the interval \([0, \pi]\) . State each answer correct to two decimal places. $$ \cos x=x $$

Short Answer

Expert verified
The solution is approximately \( x = 0.74 \) within the interval \([0, \pi]\).

Step by step solution

01

Understand the Problem

We need to find all solutions of the equation \( \cos x = x \) in the interval \([0, \pi]\). This means we are looking for the values of \( x \) such that when \( x \) is plugged into the cosine function, it results in the same value as \( x \).
02

Plot the Graphs

To understand how the solutions behave over the interval \([0, \pi]\), plot the graphs of \( y = \cos x \) and \( y = x \). The solutions to the equation correspond to the intersection points of these two graphs in the given interval.
03

Identify Intersection Points

Since this is a transcendental equation, it's best solved graphically or using numerical methods. From the plot, look for any points where the two graphs intersect within the interval \([0, \pi]\).
04

Use Numerical Methods

Use a numerical method, such as the bisection method or Newton's method, to find the intersection points. These points are the solutions for \( x \) where \( \cos x = x \).
05

Refine and Validate Solutions

After finding the approximate solutions using numerical methods, refine them to ensure they are correct to two decimal places and confirm that they lie within the given interval.
06

Determine and State Solutions

Based on the graphical solutions along with the numeric confirmations, determine the \( x \) values where \( \cos x = x \) holds true. These solutions are the intersections between the two functions.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Transcendental Equations
A transcendental equation is one that goes beyond algebraic expressions like polynomials. The equation \( \cos x = x \) is a classic example. Here, we have a trigonometric function (cosine) equated to a linear term \( x \). Transcendental equations don't have straightforward algebraic solutions. This is because the nature of these functions makes it impossible to express \( x \) using a finite number of algebraic operations. Instead, these equations are typically solved using methods like graphs or numerical approximation, because traditional algebraic techniques fall short.
When solving transcendental equations, having a solid understanding of the functions involved is crucial. You'll usually be seeking out intersection points, which leads us to exploring graphical solutions or using numerical techniques for precision.
Numerical Methods
Numerical methods are powerful tools for finding approximate solutions to equations when direct algebraic solutions are not feasible. In cases like the equation \( \cos x = x \), where we need a solution to two decimal places, methods such as the bisection method or Newton's method are invaluable.
  • Bisection Method: This method involves selecting two initial points where the function changes sign. By dividing the interval and honing in on the zero of the function, it converges to the solution.
  • Newton's Method: A faster approach, this method uses derivatives to rapidly home in on the root. It's especially effective with smooth, continuous functions.
By systematically applying these numerical techniques, you can refine your solutions until they're precise enough to satisfy the problem's requirements. Remember always to check that the solutions obtained fall within the desired interval, in this case, \([0, \pi]\).
Graphical Solutions
Graphical solutions involve visualizing equations to find their intersection points. For \( \cos x = x \), plotting both \( y = \cos x \) and \( y = x \) on the same graph can offer immediate insights.
This graphical analysis shows us where the two functions meet by intersecting each other. Within the interval \([0, \pi]\), the intersection points are where the solutions to the equation lie. Observing a graph can help you identify these points visually, turning a complex equation into something more intuitive. Whether you're confirming solutions or simply needing to guess a starting point for numerical methods, graphical solutions are indispensable. Often, they're used in conjunction with numerical techniques to ensure accuracy.
Intersection Points
The concept of intersection points is central to solving equations like \( \cos x = x \). An intersection point is where two curves meet, sharing the same \( x \) and \( y \) coordinates. For transcendental equations, this often means finding shared values that satisfy both equations involved.
In \( y = \cos x \) and \( y = x \), determining their intersection point within \([0, \pi]\) tells us exactly where these two functions "agree" on their output. The challenge lies in locating this point either through graphical inspection or numerical calculation. When solved accurately, these intersection points represent the true solutions of the initial equation. It's crucial to ensure that these solutions adhere to the specified interval and accuracy, typically expressed to a specific number of decimal places as required by the problem.

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