Hello,

I have a problem from Evans_partial differantial equations. Ch 2.23

Let S denote the square lying in R x (0,∞)with corners at the points (0,1), (1,2), (0,3), (-1,2). Define

f(x,t)= -1 for (x,t) ԑ S ∩ {t>x+2}

1 for (x,t) ԑ S ∩ {t<x+2}

0 otherwise

Assume u solves

u_{tt}-u_{xx}=f in R x (0,∞)

u=0, u_{t}=0 on R x {t=0}

Describe the shape of u for times t>3.

(J. G. Kingston, SIAM Review 30 (1988), 645-649)

I would be appreciated if anyone helpe me. Thank you