Solve the wave equation (2) in Section 12.8 a²u + (2) ax² дуг at² subject to the given conditions. u(0, y, t) 0, u(л, y, t) = 0 = u(x, 0, t) = 0, u(x, π, t) = 0 u(x, y, 0) = xy(x - л)(у - π) ди at t = 0 = 0 u(x, y, t) = Ï Ï m = 1 n = 1 sin(mx) sin(ny)