Solve the equation ut = uxx with the boundary conditions u(x,0) = 3 sin (n x) and u(0,t)=0=u(1,t) where 0<x<1 and t>0.

• A. (3 _{n=1}^ ) e^{-n² ² t} cos u2061(n x)
• B. ( _{n=1}^ ) e^{-n² ² t} sin u2061(n x)
• C. (3 _{n=1}^ ) e^{-n² ² t} sin u2061(n x)
• D. ( _{n=1}^ ) e^{-n² ² t} cos(n x)