# Rectangular Drum Problem #9

Just #9, please.

Solve the rectangular drum problem

u_xx + u_yy = (c^-2)u_tt 0 < x < a 0 < y < b t > 0

u(x,y,t) = 0, u(a,y,t) = 0 0 < y < b t > 0

u(x,0,t) = 0, u(x,b,t) = 0 0 < x < a t> 0

u(x,y,0) = xy and (u_t)(x,y,0) = 0.

Find the solution explicitly in the case

u(x,y,0) = xy and (u_t)(x,y,0) = 0.

https://brainmass.com/math/numerical-analysis/rectangular-drum-problem-30778

#### Solution Preview

First we assume that:

u(x,y,t)=X(x)Y(y)T(t), so if we plug this into the equation, we will get:

X"YT+Y"XT=(1/c^2)T"XY or

X"/X+Y"/Y=(1/c^2)T"/T or

X"/X=-Y"/Y+(1/c^2)T"/T

We let the above expression be -k1^2 in that case we will have:

X"/X=-k1^2

X(x)=Acos(k1x)+Bsin(k1x)

Ok, because u(0,y,t)=X(0)Y(y)T(t)=0 ---> ...

#### Solution Summary

In this solution, a rectangular drum problem is solved. A Word copy of the solution is also attached.

$2.19