>> clear
>> [iL,uC]=dsolve('D2iL+5*DiL+4*iL=4*heaviside(t),0.25*D2iL=DuC','iL(0)=0,uC(0)=0','t')
iL =
-(exp(-4*t)*(4*exp(3*t)*((4*C4)/3 - (4*heaviside(t)*(exp(t) - 1))/3) - (16*C4)/3 + (4*heaviside(t)*(exp(4*t) - 1))/3))/4
uC =
(exp(-4*t)*(exp(3*t)*((4*C4)/3 - (4*heaviside(t)*(exp(t) - 1))/3) - (16*C4)/3 + (4*heaviside(t)*(exp(4*t) - 1))/3 + 4*C4*exp(4*t)))/4
由于这两个式中含有多个未知数,用plot或ezplot都是画不出图形的。要画出图,须先把式中的未知数减少到1个。