ickness = 3);with(plots)animate3d(cos(t*x)*sin(3*t*y), x = -Pi .. Pi, y = -Pi .. Pi, t = 1 .. 2)
求解偏微分方程组.求解偏微分方程组条件为formula_52.答案： <math>v \left( x,t \right) ={e^{\sqrt {\it \_C3}\,{e^{\it \_C1}+{\frac , \ \ u \left( x,t