主题:求教解方程并积分的问题
%有一个我很头疼的问题,解如下微分方程
clc
syms x1 x2 t R a
v=sin(t)+2*sin(2*t)
E=dsolve('Dx1=x2','Dx2=-2*2000^2*(x1-sin(t)-sin(2*t))-2*2000*x2', 'x1(0)=0','x2(0)=0 ')
x1=E.x1
x2=E.x2
%再做如下运算
T=50
a11=int(x2,0,T)
a=int((diff(sin(t)+2*sin(2*t), t)), 0, T)
b=a-a11
b=double(b)
%结果为
%b =
% -0.5050
% 而将积分中的x2变为x2^2,以及(diff(sin(t)+2*sin(2*t), t)变为(diff(sin(t)+2*sin(2*t), t)^2, 后
v=sin(t)+2*sin(2*t)
E=dsolve('Dx1=x2','Dx2=-2*2000^2*(x1-sin(t)-sin(2*t))-2*2000*x2', 'x1(0)=0','x2(0)=0 ')
x1=E.x1
x2=E.x2
T=50
a11=int(x2^2,0,T)
a=int((diff(sin(t)+2*sin(2*t), t))^2, 0, T)
b=a-a11
b=double(b)
%结果却是
b =
297.6935
这应该没有这么大的差距
不知我哪出错了,肯请指教
clc
syms x1 x2 t R a
v=sin(t)+2*sin(2*t)
E=dsolve('Dx1=x2','Dx2=-2*2000^2*(x1-sin(t)-sin(2*t))-2*2000*x2', 'x1(0)=0','x2(0)=0 ')
x1=E.x1
x2=E.x2
%再做如下运算
T=50
a11=int(x2,0,T)
a=int((diff(sin(t)+2*sin(2*t), t)), 0, T)
b=a-a11
b=double(b)
%结果为
%b =
% -0.5050
% 而将积分中的x2变为x2^2,以及(diff(sin(t)+2*sin(2*t), t)变为(diff(sin(t)+2*sin(2*t), t)^2, 后
v=sin(t)+2*sin(2*t)
E=dsolve('Dx1=x2','Dx2=-2*2000^2*(x1-sin(t)-sin(2*t))-2*2000*x2', 'x1(0)=0','x2(0)=0 ')
x1=E.x1
x2=E.x2
T=50
a11=int(x2^2,0,T)
a=int((diff(sin(t)+2*sin(2*t), t))^2, 0, T)
b=a-a11
b=double(b)
%结果却是
b =
297.6935
这应该没有这么大的差距
不知我哪出错了,肯请指教