Consider the vibrating system described by the initial value problem. (A computer algebra system is recommended.) u'' + u = 8 co

Step-by-step explanation:

We are dealing with the differential equation

This can be approached using the method of undetermined coefficients. The overall solution is

u(t) = uh(t) + up(t)

where uh(t) represents the solution to the homogeneous part, and up(t) is a particular solution.

1. To start, let's find uh(t) using the characteristic polynomial:

The roots are imaginary:

r1=+i

r2=-i

Thus, uh(t) can be expressed as

where A and B are constants that need to be determined.

2. Next, we establish up(t). Using the method of undetermined coefficients, we can guess that up(t)=Ccos(wt)+Dsin(wt). Taking its derivatives gives us

Substituting this into the differential equation yields

From here, we obtain

As it turns out, we set D=0 since the solution does not concern sin functions.

3. Ultimately, the expression for u(t) is

When we apply the initial conditions, we find

Answer:

u(t)  = -(3 + w^2 ) cos t /(1- w^2)cos t + 7 sin t + 8 cos wt /(1- w^2)

Step-by-step explanation:

The characteristic equation is k² + 1 = 0, which leads to k² = -1, resulting in k = ±i.

The roots are k = i or -i.

The general solution takes the form  u(x)=C₁cosx+C₂sinx.

Applying the method of undetermined coefficients, we have

Uc(t) = Pcos wt  + Qsin wt

Calculating the derivatives gives us Uc’(t) = -Pwsin wt  + Qwcos wt

And differentiating again yields Uc’’(t) = -Pw^2cos wt  - Qw^2sin wt

With the equation U’’ + u = 8cos wt, we substitute:

-Pw^2cos wt  - Qw^2sin wt + Pcos wt  + Qsin wt = 8cos wt.

This simplifies to (-Pw^2 + P) cos wt   + (-Qw^2 + Q) sin wt = 8cos wt.

From -Pw^2 + P = 8, we find P= 8  /(1- w^2).

From -Qw^2 + Q = 8, we can conclude Q = 0.

Thus, Uc(t) = Pcos wt  + Qsin wt = 8 cos wt /(1- w^2).

Combining gives us U(t) = uh(t ) + Uc(t)

     = C1cos t + c2 sin t + 8 cos wt /(1- w^2).

Initial conditions yield:

U(0) = C1cos(0) + c2 sin (0) + 8 cos (0) /(1- w^2)

Which leads us to C1 + 8 /(1- w^2) = 5

So C1 = 5 - 8 /(1- w^2) = -(3 + w^2 ) /(1- w^2).

Next, taking the derivative:

U’(t) = -C1 sin t + c2 cos t - 8 w sin wt /(1- w^2).

Evaluating at t = 0 gives us:

U’(0) = -C1 sin (0) + c2 cos (0) - 8 w sin (0) /(1- w^2) = 7.

Thus, c2 = 7.

  u(t)  = -(3 + w^2 ) cos t /(1- w^2)cos t + 7 sin t + 8 cos wt /(1- w^2)