Error in solving equation

    syms m_c0 j_L0 theta1 M m_c_gama j_L_gama j_L_theta1 m_c_theta2 _L_theta2 
syms m_c_theta1 gama l  theta2 k1
eqn1=m_c_theta1==(m_c0-1/M+1)*cos(theta1)+j_L0*sin(theta1)+1/M-1;
eqn2=j_L_theta1==(-m_c0+1/M-1)*sin(theta1)+j_L0*cos(theta1);
%eqn3=m_m_theta1==1;
%eqn3=j_Lm_theta1==j_Lm0+l*theta1;
eqn4=m_c_theta2==j_L_theta1*sin(theta2-theta1)+(m_c_theta1+1)*cos(theta2-theta1)-1;
eqn5=j_L_theta2==j_L_theta1*cos(theta2-theta1)-(m_c_theta1+1)*sin(theta2-theta1);
%m_m_theta2=1;
%qn6=j_Lm_theta2==j_Lm0+l*theta2;
eqn7=m_c_gama==(1/k1)*j_L_theta2*sin(k1*(gama-theta2))+m_c_theta2*cos(k1*(gama-theta2));
eqn8=j_L_gama==j_L_theta2*cos(k1*(gama-theta2))-k1*m_c_theta2*sin(k1*(gama-theta2));
%eqn9=j_Lm_gama==j_L_gama;
%m_m_gama=(-m_c_theta2*cos(k1*(gama-theta2))-(1/k1)*j_L_theta2*sin(k1*(gama-theta2)))/(1+l)
m_c_gama=-m_c0;
j_L_gama=-j_L0;
j_L_theta2=(gama*l)/2;
%j_L_theta2=j_Lm_theta2;
%j_Lm0=-j_Lm_gama;
%j_L_gama=j_Lm_gama;
eqns = subs([eqn1, eqn2, eqn4, eqn5, eqn7, eqn8]);
sol = solve(eqns, m_c0, j_L0, m_c_theta1,j_L_theta1,m_c_theta2,j_L_theta2)

this is showing some errors like this:

Error using sym.getEqnsVars>checkVariables (line 92) The second argument must be a vector of symbolic variables.

Error in sym.getEqnsVars (line 62) checkVariables(vars);

Error in solve>getEqns (line 450) [eqns, vars] = sym.getEqnsVars(argv{:});

Error in solve (line 225) [eqns,vars,options] = getEqns(varargin{:});

Error in eqnsolve_highvolfullload (line 28) sol = solve(eqns, m_c0, j_L0, m_c_theta1,j_L_theta1,m_c_theta2,j_L_theta2,theta1, theta2)

what should be done?

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/325491-error-message-in-solving-symbolic-equation