# Differential Equations: Lecture 1.1-1.2 Definitions and Terminology and Initial Value Problems | Summary and Q&A

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January 9, 2020
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Differential Equations: Lecture 1.1-1.2 Definitions and Terminology and Initial Value Problems

## TL;DR

Learn about differential equations, which involve unknown functions and their derivatives, and how to solve initial value problems.

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### Q: What is a differential equation and how is it different from a regular equation?

A differential equation is an equation that involves an unknown function and one or more of its derivatives. Unlike a regular equation, which only involves variables and constants, a differential equation involves the rate of change of a function.

### Q: How are ordinary and partial differential equations different?

Ordinary differential equations involve derivatives with respect to a single variable, while partial differential equations involve derivatives with respect to multiple variables. Ordinary differential equations describe systems that change over time, while partial differential equations describe the behavior of functions in multiple dimensions.

### Q: What is the order of a differential equation and how is it determined?

The order of a differential equation is determined by the highest derivative involved in the equation. For example, a second-order differential equation involves the second derivative of the unknown function, while a first-order equation involves the first derivative.

### Q: What is a one-parameter family of solutions and how is it related to the general solution?

A one-parameter family of solutions represents a set of solutions to a differential equation that can be obtained by varying a single free parameter. The general solution refers to the entire collection of all possible solutions, which may include multiple families of solutions.

### Q: What is a particular solution in an initial value problem and how is it determined?

A particular solution in an initial value problem is a specific solution that satisfies both the differential equation and a given initial condition. By substituting the initial condition into the general solution and solving for the constant, the particular solution can be found.

### Q: What is the interval of definition in an initial-value problem and how is it identified?

The interval of definition in an initial-value problem is the largest interval over which the solution to the differential equation is defined. It is determined by examining the behavior of the solution and any restrictions imposed by the differential equation itself.

### Q: Explain the concept of a singular solution in the context of a differential equation.

A singular solution is a solution to a differential equation that cannot be obtained by varying the free parameters in the general solution. It is characterized by a specific value or behavior that is distinct from the rest of the solutions.

### Q: How do you solve an initial value problem and find the particular solution?

To solve an initial value problem, you first need to find the general solution of the differential equation. Then, substitute the initial condition into the general solution and solve for the constant(s). This yields the particular solution that satisfies both the differential equation and the given initial condition.

## Summary & Key Takeaways

• A differential equation is an equation with an unknown function and one or more of its derivatives.

• There are two types of differential equations: ordinary and partial, depending on whether they involve ordinary or partial derivatives.

• The order of a differential equation is determined by the highest derivative involved.

• Questions:

1. What is a differential equation and how is it different from a regular equation?

2. How are ordinary and partial differential equations different?

3. What is the order of a differential equation and how is it determined?

4. What is a one-parameter family of solutions and how is it related to the general solution?

5. What is a particular solution in an initial value problem and how is it determined?

6. What is the interval of definition in an initial value problem and how is it identified?

7. Explain the concept of a singular solution in the context of a differential equation.

8. How do you solve an initial value problem and find the particular solution?

### Q: What is a differential equation and how is it different from a regular equation?

A differential equation is an equation that involves an unknown function and one or more of its derivatives. Unlike a regular equation, which only involves variables and constants, a differential equation involves the rate of change of a function.