# Solve first ode using ode45

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Lim Xiao Hui on 9 Jun 2021
Commented: Lim Xiao Hui on 9 Jun 2021
Hello, my question is i have first ode dT/dt = -0.0004*[T(t) - 5], may i know how to use ode45 to solve t in the range T [8 88]? Can i know how about the script? Thank you for your help.

Walter Roberson on 9 Jun 2021
format long g
syms T(t) T8
dTdt = diff(T(t),t)
dTdt = eqn = dTdt == -0.0004*(T - 5)
eqn(t) = init = T(8) == T8
init = sol = simplify(dsolve([eqn, init]))
sol = Specific_T8 = 6
Specific_T8 =
6
Tsol = subs(sol, T8, Specific_T8)
Tsol = fplot(Tsol, [8 88]) ##### 1 CommentShowHide None
Lim Xiao Hui on 9 Jun 2021
thank you

Jan on 9 Jun 2021
Edited: Jan on 9 Jun 2021
You can modify the examples of the documentation easily, see: doc ode45
Temperature0 = 6.2; % Your initial value
[Time, Temperatur] = ode45(@fcn, [8, 88], Temperature0)
plot(Time, Temperature);
function dT = fcn(Time, Temperature)
dT = -0.0004 * (Temperatur - 5);
end
##### 1 CommentShowHide None
Lim Xiao Hui on 9 Jun 2021
thank you