Using D'Alembert method on

$\frac{1}{2}sinxcost+4$xtsinxcost$+2$xtsin$(x+t)+{\displaystyle \underset{x-t}{\overset{x+t}{}}}xdx{u}_{tt}=u_{},-$

$We$ get

$\frac{1}{2}sinxcost+4xt$

$b.sinxcost+2xt.$

$sin(x+t)+{\displaystyle \underset{x-t}{\overset{x+t}{}}}xdx$

$d.$ None $.$