Solve a group of Symbolic Equations

syms A B alpha beta               % variable
syms R1 R2 C1 C2                  % constant
eqn1 = A + B == 1/(R1*C1)

eqn1 = 

eqn2 = -A*beta-B*alpha == 0

eqn2 = 

eqn3 = alpha*beta == 1/(R1*C1*R2*C2)

eqn3 = 

eqn4 = (R1*C1+R1*C2+R2*C2)/(R1*C1*R2*C2) == -alpha-beta

eqn4 = 

[A,B,alpha,beta] = solve(eqn1,eqn2,eqn3,eqn4)

A = 

B = 

alpha = 

beta = 

A1 = simplify(A)

A1 = 

B1 = simplify(B)

B1 = 

alpha1 = simplify(alpha)

alpha1 = 

beta1 = simplify(beta)

beta1 = 

I want to get A1,B1,alpha1,beta1 represented only by constant (R1 R2 C1 C2). However, when I run the codes, the system gives me:

A1 =

1/(C1*(A + B))

1/(C1*(A + B))

B1 =

-(A^2*C1 + B^2*C1 - A*(C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) + B*(C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) + 2*A*B*C2)/(2*A*B*C1*C2*(A + B))

-(A^2*C1 + B^2*C1 + A*(C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) - B*(C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) + 2*A*B*C2)/(2*A*B*C1*C2*(A + B))

alpha1 =

((A + B)*((C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) + A*C1 - B*C1))/(2*B*(C1 + C2))

-((A + B)*((C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) - A*C1 + B*C1))/(2*B*(C1 + C2))

beta1 =

-((A + B)*((C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) + A*C1 - B*C1))/(2*A*(C1 + C2))

((A + B)*((C1*(A^2*C1 + B^2*C1 + 2*A*B*C1 + 4*A*B*C2))^(1/2) - A*C1 + B*C1))/(2*A*(C1 + C2))

What other codes should I add to solve this problem?

Answer 1

[Dyuman Joshi]

You need to specify which variables are you solving for -

syms A B alpha beta               % variable
syms R1 R2 C1 C2                  % constant
eqn1 = A + B == 1/(R1*C1);
eqn2 = -A*beta-B*alpha == 0;
eqn3 = alpha*beta == 1/(R1*C1*R2*C2);
eqn4 = (R1*C1+R1*C2+R2*C2)/(R1*C1*R2*C2) == -alpha-beta;
[A0,B0,alpha0,beta0] = solve([eqn1,eqn2,eqn3,eqn4],[A, B, alpha, beta]);
A0

A0 = 

B0

B0 = 

alpha0

alpha0 = 

beta0

beta0 = 

Answer 2

[Walter Roberson]

You have four equations in 8 unknowns. When you call solve() you should specify the names of the variables to solve for. solve() is not able to read the names of the variables you are assigning to in order to figure out which variables you want to solve for.