@Carl Love 

thanks of your help.

@gkokovidis 

thanks of your help.

@Carl Love 

Thank you so much my friend...

@Carl Love 

all initial conditions are zero.

@Carl Love 

tnx of your answer,but infact i have two nonlinear ODE(second order) in terms of f(x)&g(x) and solve them with dsolve,numeric,now i will plot f(x)-g(x) for 0<x<1????? 

my equations:

EQ1 := -1.383117238*10^(-9)*g(x)+3.982412158*10^(-19)*f(x)^3+4.345190954*10^(-9)*f(x)+3.643814675*10^(-17)*(diff(f(x), x, x)) = 0
EQ2 := 3.522088319*10^(-10)*g(x)-1.106493792*10^(-9)*f(x)^2+2.429209785*10^(-24)*(diff(g(x), x, x)) = 0
res := dsolve(`union`(eval({EQ1, EQ2}), {f(0) = 0.1e-1, g(0) = 0, (D(f))(0) = 0, (D(g))(0) = 0}), numeric, maxfun = 0)

now i will plot f(x)-g(x) for 0<x<1????? 

@Carl Love

tnx of your answer,but infact i have two nonlinear ODE(second order) in terms of f(x)&g(x) and solve them with dsolve,numeric,now i will plot f(x)-g(x) for 0<x<1????? 

@mehdi jafari 

tnx of your answer...

when i use the dsolve for solve my problem with numeric method i can not plot values for a function after t>2,how solve this problem?the maple error,maxfun is exceeded while i use the max value for maxfun....

@Carl Love 

numeric solution........

@Markiyan Hirnyk 

thanks of your answer but when i use the command f := DirectSearch:-DataFit(A*cos(x*omega1+phi1)*sin(omega2*x), XY[() .. (), 1], XY[() .. (), 2], x, initialpoint = [A = 0.5e-1, omega1 = evalf(2*Pi/(0.1e-1)), omega2 = 10*evalf(2*Pi/(0.1e-1)), phi1 = 0], fitmethod = lms) i see the below error :

Error, `DirectSearch` does not evaluate to a module

?????????????????????????????????????????????????

@Kitonum 

THANKS OF YOUR ANSWER...

i have a question of you,infact i must find my response from plot,are there methods for it in maple?

@Carl Love 

Hi:

I attach my problem in maple file(.mw),and i should find the math equation for plots(q1,q2,q4).

EQUATIONS(linear).mw

@Preben Alsholm 

thanks Dear Preben Alsholm...

@Preben Alsholm 

thanks of your answer :

my initial conditions for this problem are:

q1(0) = 0.1e-2, q2(0) = 0, q3(0) = 0, q4(0) = 0, q5(0) = 0, (D(q1))(0) = 0, (D(q2))(0) = 0, (D(q3))(0) = 0, (D(q4))(0) = 0, (D(q5))(0) = 0

what means of T0 ?

thanks of your answer :

my initial conditions for this problem are:

q1(0) = 0.1e-2, q2(0) = 0, q3(0) = 0, q4(0) = 0, q5(0) = 0, (D(q1))(0) = 0, (D(q2))(0) = 0, (D(q3))(0) = 0, (D(q4))(0) = 0, (D(q5))(0) = 0