Question

MATLAB解微分方程，为什么将上一步计算出的值带入到下一步计算？

syms t;
y = 2 + 3 * sin(4 * t + pi / 4);
x = dsolve('Dx + l * x - y == 0', 'x(0) == 0', 't')
xf = dsolve('k * Dxf + xf - x == 0', 'xf(0) == 0', 't')

>>x =
(y - y*exp(-l*t))/l

xf =
x - x*exp(-t/k)

Answer 1

要完成你的问题。首先，声明变量要完整，即syms t k；其二，已知x的表达式，计算xf，应用eval（）函数命令来计算，即xf=eval(xf)。完整的代码如下：

syms t k

 y = 2 + 3 * sin(4 * t + pi / 4);

x = dsolve('Dx + l * x - y = 0', 'x(0) = 0', 't')

 xf = dsolve('k * Dxf + xf - x = 0', 'xf(0) = 0', 't')

xf=eval(xf)

执行结果