Solve this differential equation: NSK PSKy''-7y'+10y=\cos xZSK NSK where y is a one-variable function

interdicoxd

interdicoxd

Answered question

2021-12-07

Solve this differential equation:
y7y+10y=cosx
where y is a one-variable function x. What am I supposed to do with the cosx?

Answer & Explanation

Ethan Sanders

Ethan Sanders

Beginner2021-12-08Added 35 answers

You can solve by means of complex numbers, generalizing to
As you know that the derivatives of the exponential are the same exponential times a coefficient, the solution must be of the form ceix. Then
(i27i+10)ceix=eix
and c=197i=9+7i130
Finally, the solution is the real part of ceix, or
9cosx7sinx130
redhotdevil13l3

redhotdevil13l3

Beginner2021-12-09Added 30 answers

For the homogeneous part, I am sure that you do not face any problem.
Now, suppose that the solution is
y=Asin(x)+Bcos(x)
y=Acos(x)Bsin(x)
y=Asin(x)Bcos(x)
and replace to get
(9A+7B)sin(x)+(9B7A)cos(x)=cos(x)
Identify; this gives
9A+7B=0
9B7A=1
Solve for A,B.
Just to make the problem more general, consider the equation
y+ay+by=csin(x)+dcos(x)
and just do the same as above. You will end with
aB+A(b1)c=0
aA+(b1)Bd=0

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?