1st order linear diff equation clarification

  • Thread starter differeq
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The initial condition y(-2) = 1 is not related to the largest interval on which a unique solution exists. The largest interval is determined by the points where the coefficient of y, p(t), is undefined or infinite. In this case, p(t) is defined for all real numbers, so the largest interval on which a unique solution exists is - infinity < t < infinity.
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differeq
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Homework Statement


determine the largest interval on which a unique solution exists:

y' + (t/((t^2)+1)) y = sin t with initial conditions: y(-2) = 1


Homework Equations


arent there discontinuities at t = 0 and t = -1?
(textbook says no, based on answer..i am confused why not?) i think it may have something to do with not understanding how the initial conditions, eg, y(-2) = 1 relate to the interval.

The Attempt at a Solution


the equation is already in the form y' + p(t)y = g(t)
p(t) = (( t/(t^2 ))+1))

if there are discont @ t = 0 and t= -1, then the intervals would be:
(- infin, -1)
(-1, 0)
(0, infin)

therefore largest interval for t = -2 is: - infin < t < -1

the answer in back though says largest interval is: - infin < t < infin

please help, thanks alot.

EDIT: i glossed over the square of t, so i now know that t= -1 does not make p(t) = 0.. but i am still unclear as to why t = 0 is not a discontinuity.. Also, i think i am unclear about what precisely is a discontinuity. thanks again for any help..
 
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  • #2
differeq said:

Homework Statement


determine the largest interval on which a unique solution exists:

y' + (t/((t^2)+1)) y = sin t with initial conditions: y(-2) = 1


Homework Equations


arent there discontinuities at t = 0 and t = -1?
(textbook says no, based on answer..i am confused why not?) i think it may have something to do with not understanding how the initial conditions, eg, y(-2) = 1 relate to the interval.

The Attempt at a Solution


the equation is already in the form y' + p(t)y = g(t)
p(t) = (( t/(t^2 ))+1))

if there are discont @ t = 0 and t= -1, then the intervals would be:
(- infin, -1)
(-1, 0)
(0, infin)

therefore largest interval for t = -2 is: - infin < t < -1

the answer in back though says largest interval is: - infin < t < infin

please help, thanks alot.

EDIT: i glossed over the square of t, so i now know that t= -1 does not make p(t) = 0.. but i am still unclear as to why t = 0 is not a discontinuity.. Also, i think i am unclear about what precisely is a discontinuity. thanks again for any help..

Your function p(t) is defined and continuous for all real numbers. Why would you think there is a problem at t = 0?
 

Related to 1st order linear diff equation clarification

1. What is a 1st order linear differential equation?

A 1st order linear differential equation is a mathematical equation that describes the relationship between a variable and its derivative. It is called "linear" because it contains only linear terms, meaning the variable and its derivative are raised to the first power.

2. How do you solve a 1st order linear differential equation?

To solve a 1st order linear differential equation, you need to use a method called "separation of variables." This involves isolating the variable and its derivative on opposite sides of the equation and then integrating both sides. The resulting solution will include an arbitrary constant, which can be determined by using initial conditions or boundary conditions.

3. What is an "initial value problem" in the context of 1st order linear differential equations?

An initial value problem is a type of boundary condition where the value of the dependent variable and its derivative are known at a specific point, typically denoted as x = a. This information is used to determine the value of the arbitrary constant in the solution to the differential equation.

4. Can a 1st order linear differential equation have multiple solutions?

Yes, a 1st order linear differential equation can have multiple solutions. This is because the solution to a differential equation includes an arbitrary constant, which can take on different values. However, if initial conditions are given, the solution will be unique.

5. How are 1st order linear differential equations used in science?

1st order linear differential equations are used in many areas of science, particularly in physics and engineering, to model and predict the behavior of systems. They can be used to describe the rate of change of physical quantities, such as velocity or temperature, over time. They are also used in fields such as biology and economics to study population growth and economic trends, respectively.

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