Hello guys...

please help me to solve these equation.I have some equation with some boundary condition.

Why can't I have good results for it?
q3:=-0.1080877976e-1:
q2:=0.04351279185:
q1:=-0.7037638761e-1:
q0:=0.05575044494:
c:=3:

eq := q3*m^6+q2*m^4+q1*m^2+q0;
rishe := solve(eq = 0, m);
a := 1/(2*c); rho := a/`#msub(mi("t"),mn("1"))`;
f0 := evalf(cosh(abs(rishe[1])*xi));
f1 := evalf(cosh(abs(Re(rishe[3]))*xi)*cos(abs(Im(rishe[3]))*xi));
f2 := evalf(sinh(abs(Re(rishe[3]))*xi)*sin(abs(Im(rishe[3]))*xi));
pin := C0*k0*f0+C1*f1+C2*f2;
ppin := diff(pin, xi); pis := C0*f0+(k1*C1+C2*k2)*f1+(C2*k1-k2*C1)*f2;
pin1 := evalf(subs(xi = a, pin));
pin2 := evalf(subs(xi = -a, pin));
pin3 := evalf(subs(xi = a, ppin));
pin4 := evalf(subs(xi = -a, ppin));
pis1 := evalf(subs(xi = a, pis));
pis2 := evalf(subs(xi = -a, pis));
hal := solve({pin1 = sigma01xx, pin2 = sigma01xx, pin3 = 0, pin4 = 0, pis1 = sigma01xy, pis2 = sigma01xy}, {C0, C1, C2, k0, k1, k2});
how can I have a good result with this method?
please help me to solve this multi equations multi variable.

Hello guys ...

I used a numerically method to solve couple differential equation that it has some boundary conditions. My problem is that some range of answers has 50% error . Do you know things for improving our answers in maple ?

my problem is :

a*Φ''''(x)+b*Φ''(x)+c*Φ(x)+d*Ψ''(x)+e*Ψ(x):=0

d*Φ''(x)+e*Φ(x)+j*Ψ''(x)+h*Ψ(x):=0

suggestion method by preben Alsholm:

a,b,c,d,e,j,h are constants.suppose some numbers for these constants . I used this code:


VR22:=0.1178*diff(phi(x),x,x,x,x)-0.2167*diff(phi(x),x,x)+0.0156*diff(psi(x),x,x)+0.2852*phi(x)+0.0804*psi(x);
VS22:=0.3668*diff(psi(x),x,x)-0.0156*diff(phi(x),x,x)-0.8043*psi(x)-0.80400*phi(x);
bok:=evalf(dsolve({VR22=0,VS22=0}));

PHI,PSI:=op(subs(bok,[phi(x),psi(x)]));
Eqs:={eval(PHI,x=1.366)=1,eval(diff(PHI,x),x=1.366)=0,eval(PHI,x=-1.366)=1,eval(diff(PHI,x),x=-1.366)=0,
eval(PSI,x=1.366)=1,eval(PSI,x=1.366)=1};
C:=fsolve(Eqs,indets(%,name));
eval(bok,C);
SOL:=fnormal(evalc(%));


I used digits for my code at the first of writting.

please help me ... what should i do?

Hello guys

I have a problem in runge kutta method for coupled differential equations .For example consider these equations:

a*Φ''''(x)+b*Φ''(x)+c*Φ(x)+d*Ψ''(x)+e*Ψ(x):=0

d*Φ''(x)+e*Φ(x)+j*Ψ''(x)+h*Ψ(x):=0

The boundry conditions are:

Φ(0.83)=1;Φ'(0.83)=0;Φ(-0.83)=1;Φ'(-0.83)=0;Ψ(0.83)=1;Ψ(-0.83)=1

Φ(x) and Ψ(x) are unknown functions and a,b,c,d,e,j,h are constants . I want to get answers by runge kutta numerical method .

i used this form of algorithm but i cant do it :

please help me to solve these types of equations.

Plz help me friends ...

I gave this function ...

fuction_A.docx

i wanna extract coeffitions from this function ... for example what is the coeffition of phi(X)*psi(x)?

i used coeff ... but it had an error ..

unable compute coeff ...

i used collect ... but it had an error

what am i doing with this problem?

:(