U(x,t)= 2/3f(x+t)+1/3f(x-2t)+(1/3pi)(sin(pi(x+t))+(1/3pi)(sin(pi(x-2t)),

f(x)=1-x,abslutex<1, zero otherwise

d2u/dt2-(2*d2u/x2)+d2u/dxdt=0    

initial condition: u(x,0)=1-x, abslute x<1   Ut(x,0)=cos(pix), bslute x<1 

B.C U(-4,t)=U(4,t)=0,   delta x=0.1, delta t=0.025, range 0..4