# Wave equation: intial conditions

#### Undoubtedly0

1. The problem statement, all variables and given/known data

Solve the initial boundary value problem

$$u_{tt}=c^2u_{xx}$$
$$u(-a,t)=0,\quad u(a,t)=0,\quad u(x,0)=\sin(\omega_1 x)-b\sin(\omega_2x)$$

where $a, b, \omega_1, \omega_2$ are positive constants.

2. Relevant equations

d'Alembert's solution

3. The attempt at a solution

Are these initial/boundary conditions enough to fully solve the problem? All of the text books I have seen address only the case where $u(x,0)$ and $u_t(x,0)$ is also given. Or possibly d'Alembert's general solution is not good to use here? Thanks all!

Related Calculus and Beyond Homework News on Phys.org

#### fishistheice

A second order partial differential equation requires four boundary conditions in order to be fully solved, so it might be the case that you are meant to assume that ut(x,0)=0. Is that all of the information the question gives you?

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving