Example Problem - 9.3 | 9. Euler’s Method | Mathematics - iii (Differential Calculus) - Vol 4
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9.3 - Example Problem

Practice

Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Introduction to Euler's Method

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0:00
Teacher
Teacher

Welcome class! Today, we are diving into Euler's Method. Can anyone tell me why we might need numerical methods like this?

Student 1
Student 1

Is it because some ODEs can't be solved analytically?

Teacher
Teacher

Exactly! Euler's Method helps us approximate solutions when analytical methods are too complex. It relies on using the slope to predict the next point.

Student 2
Student 2

How do we find that slope?

Teacher
Teacher

Great question! The slope is determined by the function \( f(x,y) \). We use the derivative at our current point to estimate the next value.

Student 3
Student 3

What happens if we choose a larger step size?

Teacher
Teacher

Good point! A larger step size can lead to less accurate results as we are approximating the curve with straight lines.

Teacher
Teacher

So remember: smaller step sizes lead to better accuracy but require more computations. Let's get into our example problem!

Setting Up the Problem

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0:00
Teacher
Teacher

For our example, we have \( \frac{dy}{dx} = x + y \), with \( y(0) = 1 \). Who can tell me what \( f(x, y) \) is in this case?

Student 4
Student 4

It's \( x + y \)!

Teacher
Teacher

Exactly! Now we need to set our initial conditions: \( x_0 = 0 \) and \( y_0 = 1 \). Can anyone explain why we need an initial condition?

Student 1
Student 1

We need it to kick off the calculations and have a starting point for the iterations.

Teacher
Teacher

Right! Now, let’s apply Euler’s method to compute the first approximate values at \( x = 0.1 \).

Performing the First Iteration

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0:00
Teacher
Teacher

Let’s calculate the first iteration. Using our formula, we calculate \( y_1 \): \[ y_1 = y_0 + h \cdot f(x_0, y_0) \]. What’s \( h \) again?

Student 2
Student 2

It's \( 0.1 \)!

Teacher
Teacher

Correct! Now we substitute: \( y_1 = 1 + 0.1(0 + 1) \). Can someone finish the calculation?

Student 3
Student 3

That makes \( y_1 = 1 + 0.1 = 1.1 \).

Teacher
Teacher

Well done! Now let’s move to the second iteration. Who remembers what we do next?

Continuing Iterations

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0:00
Teacher
Teacher

Now we calculate the second iteration, \( x = 0.2 \). Can anyone write down the formula for \( y_2 \)?

Student 4
Student 4

It's \( y_2 = y_1 + h \cdot f(x_1, y_1) \).

Teacher
Teacher

Exactly! Let's substitute our values: \( y_2 = 1.1 + 0.1(0.1 + 1.1) \). Can anyone compute \( y_2 \)?

Student 1
Student 1

I think \( y_2 = 1.1 + 0.12 = 1.22 \).

Teacher
Teacher

Perfect! Now let’s do it for the final iteration, \( x = 0.3 \). What do we get?

Final Results and Summary

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0:00
Teacher
Teacher

For our last iteration, we calculate: \( y_3 = y_2 + h \cdot f(x_2, y_2) \). What is our \( f(x_2, y_2) \)?

Student 2
Student 2

It's \( 0.2 + 1.22 = 1.42 \).

Teacher
Teacher

Exactly! So, \( y_3 = 1.22 + 0.1(1.42) = 1.22 + 0.142 = 1.362 \). Great job! Now, what are our final approximate values?

Student 3
Student 3

We have \( y(0.1) \approx 1.1, \; y(0.2) \approx 1.22, \; y(0.3) \approx 1.362! \)

Teacher
Teacher

Excellent! To summarize, Euler’s method provides a straightforward approach to approximating solutions of ODEs. It involves computing values step by step based on the initial point and given slope. Don’t forget that accuracy can depend on the step size. Well done, everyone!

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section demonstrates the application of Euler's method to solve a specific ordinary differential equation.

Standard

The example walks through the step-by-step process of using Euler's method to approximate solutions for a first-order ODE, highlighting iterations and the importance of step size in reaching accurate solutions.

Detailed

Detailed Summary

In this section, we discuss an illustrative example of Euler's method by solving the ordinary differential equation (ODE) given by \( \frac{dy}{dx} = x + y \) with the initial condition \( y(0) = 1 \). The task is to compute the approximate values for \( y \) at \( x = 0.1, 0.2, 0.3 \) using a step size of \( h = 0.1 \).

We begin by identifying \( f(x, y) = x + y \) and initializing with \( x_0 = 0 \) and \( y_0 = 1 \). The iterative process is outlined as follows:

  1. First Iteration (x = 0.1)
  2. Compute \( y_1 \):
    \[ y_1 = y_0 + h \cdot f(x_0, y_0) = 1 + 0.1(0 + 1) = 1 + 0.1 = 1.1 \]
  3. Second Iteration (x = 0.2)
  4. Compute \( y_2 \):
    \[ y_2 = y_1 + h \cdot f(x_1, y_1) = 1.1 + 0.1(0.1 + 1.1) = 1.1 + 0.12 = 1.22 \]
  5. Third Iteration (x = 0.3)
  6. Compute \( y_3 \):
    \[ y_3 = y_2 + h \cdot f(x_2, y_2) = 1.22 + 0.1(0.2 + 1.22) = 1.22 + 0.142 = 1.362 \]

Finally, we obtain the approximate values:
- \( y(0.1) \approx 1.1 \)
- \( y(0.2) \approx 1.22 \)
- \( y(0.3) \approx 1.362 \)

This example clearly illustrates the step-by-step nature of Euler's method and highlights its application in numerical solution of ODEs.

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Audio Book

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Problem Setup

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Problem: Use Euler’s method to solve
𝑑𝑦/𝑑𝑥 = 𝑥 + 𝑦, 𝑦(0) = 1
for 𝑥 = 0.1, 0.2, 0.3 using step size ℎ = 0.1

Detailed Explanation

In this example, we are tasked with solving a first-order ordinary differential equation (ODE) using Euler’s method. The ODE we have is written as 𝑑𝑦/𝑑𝑥 = 𝑥 + 𝑦, which describes how the variable 𝑦 changes with respect to the variable 𝑥. We know the initial condition, 𝑦(0) = 1, which means that when 𝑥 is 0, the value of 𝑦 is 1. We want to estimate the values of 𝑦 at three points: 0.1, 0.2, and 0.3, using a small step size ℎ of 0.1.

Examples & Analogies

Think of this setup as tracking the height of a plant that grows based on both its current height and the amount of sunlight it received (this is analogous to the term 𝑥 + 𝑦). You start measuring its height at time 0 (when it's 1 meter tall) and want to predict its height after 1 minute, 2 minutes, and 3 minutes while considering how tall it grows over each minute.

Step 1: First Iteration

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Step 1: First iteration (x = 0.1)
𝑦 = 𝑦 + ℎ ⋅ 𝑓(𝑥 ,𝑦 ) = 1 + 0.1(0 + 1) = 1 + 0.1 = 1.1

Detailed Explanation

In the first iteration, we start at the initial point where 𝑥 = 0 and 𝑦 = 1. We apply Euler’s method to estimate the value of 𝑦 at the next point 𝑥 = 0.1. We calculate the slope using the function 𝑓(𝑥, 𝑦) = 𝑥 + 𝑦. For 𝑥 = 0 and 𝑦 = 1, this gives us 𝑓(0, 1) = 0 + 1 = 1. We then plug this into the Euler formula: 𝑦 = 1 + 0.1 * 1, which results in 𝑦 = 1.1.

Examples & Analogies

Imagine you took a small step outside your house, and you measured the change in height of the plant. If the plant is currently 1 meter tall and grows 10 centimeters because of the sunlight at that moment, you can predict its new height (1.1 meters) after that minute.

Step 2: Second Iteration

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Step 2: Second iteration (x = 0.2)
𝑦 = 𝑦 + ℎ⋅𝑓(𝑥 ,𝑦 ) = 1.1 + 0.1(0.1 + 1.1) = 1.1 + 0.1(1.2) = 1.1 + 0.12 = 1.22

Detailed Explanation

In the second iteration, we now start with our newly calculated value of 𝑦 = 1.1 at 𝑥 = 0.1. We calculate the slope again using 𝑓(𝑥, 𝑦) with our current values: 𝑓(0.1, 1.1) = 0.1 + 1.1 = 1.2. We apply this to the Euler formula: 𝑦 = 1.1 + 0.1 * 1.2, which results in 𝑦 ≈ 1.22.

Examples & Analogies

Continuing to observe your plant, you check its height again after the second minute. It's now 1.1 meters, and with the sunlight still working its magic, it grows an additional 12 centimeters, resulting in a new height of approximately 1.22 meters.

Step 3: Third Iteration

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Step 3: Third iteration (x = 0.3)
𝑦 = 𝑦 + ℎ ⋅ 𝑓(𝑥 ,𝑦 ) = 1.22 + 0.1(0.2 + 1.22) = 1.22 + 0.1(1.42) = 1.22 + 0.142 = 1.362

Detailed Explanation

For the third iteration, we now take our latest found value of 𝑦 = 1.22 when 𝑥 = 0.2. Again, we compute the slope: 𝑓(0.2, 1.22) = 0.2 + 1.22 = 1.42. Using the Euler formula, we calculate 𝑦 = 1.22 + 0.1 * 1.42, leading to 𝑦 ≈ 1.362.

Examples & Analogies

You take another peek at your growing plant after three minutes. With the plant now at around 1.22 meters, it absorbs even more sunlight and stretches to approximately 1.362 meters tall. This growth demonstrates how changes compound over time.

Final Approximate Values

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Final Approximate Values:
• 𝑦(0.1) ≈ 1.1
• 𝑦(0.2) ≈ 1.22
• 𝑦(0.3) ≈ 1.362

Detailed Explanation

After performing the three iterations using Euler's method, we arrive at our approximate values for 𝑦 at the specified points. Our final results show that 𝑦 is approximately 1.1 when 𝑥 = 0.1, about 1.22 at 𝑥 = 0.2, and approximately 1.362 when 𝑥 = 0.3. These values give us a numerical approximation of how 𝑦 changes as we increment 𝑥.

Examples & Analogies

In the end, just like measuring the height of your growing plant at different intervals, you've collected approximations of its height at each moment (0.1 meters, 0.2 meters, and 0.3 meters), highlighting how it has steadily grown over time.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Step-by-step approximation: Euler's method computes the next value based on the current value and slope derived from the ODE.

  • Dependent variable estimation: The method allows estimation of dependent variables at specific intervals based on the initial condition.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Using the ODE \( \frac{dy}{dx} = x + y \) with an initial condition of \( y(0) = 1 \), we can estimate values step by step using Euler's method.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Euler's method, so neat and bright, step by step, it guides us right.

📖 Fascinating Stories

  • Imagine creating a staircase using Euler’s method: each step helps you climb closer to your solution, one step at a time.

🧠 Other Memory Gems

  • For Euler's method: Slope, Step, Solve - Remember: find the slope, take a step, and then solve for the next value.

🎯 Super Acronyms

ESS

  • Estimate
  • Step
  • Solve - A reminder of the key steps in Euler's method.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Ordinary Differential Equation (ODE)

    Definition:

    An equation relating a function with its derivatives. Often used to describe dynamic systems.

  • Term: Euler's Method

    Definition:

    A numerical technique for approximating solutions to first-order ordinary differential equations.

  • Term: Step Size (h)

    Definition:

    The interval at which we calculate the values of the dependent variable in numerical methods.

  • Term: Initial Condition

    Definition:

    The value of the dependent variable at a specific point, necessary to begin iterative methods.