Help with basic matlab

Abel

2013 5 14

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Thanks for reading my question

When I use dsolve in an ivp I get this ans:

dsolve('Dy = -yt + sin(3t) - cos(t.01) + 3sin(7*t)', 'y(0) = 0')

ans =

exp(-t^2/2)*int(exp(x2/2)(sin(3x) - cos(x/100) + 3sin(7x)), x = 0..t, IgnoreAnalyticConstraints)/exp(t2/2)

I would like to know how can I evaluate it in the interval t=0:h:20, dom =[0 20] if h=(5,5/2,5/4,....), if i just simply eval, matlab shows an error even if i ignore the analytic constraints.

Error using sym/eval (line 11)

Error: Unexpected MATLAB expression.

I think it is because eval does't work with integrals.

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Walter Roberson 2013-5-14

在 MATLAB Online 中打开

Your notation is a bit ambiguous. Are you attempting to do

dsolve('diff(y(t), t) = -y(t)+sin(3*t)-cos((1/100)*t)+3*sin(7*t)', 'y(0) = 0')

If you are then,

y(t) = -(3/10)*cos(3*t) + (1/10)*sin(3*t) - (10000/10001)*cos((1/100)*t) - (100/10001)*sin((1/100)*t) - (21/50)*cos(7*t) + (3/50)*sin(7*t) + (430018/250025)*exp(-t)

I do not find any useful simplifications of that.

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