Solve algebraic equation: define for which variable to solve

Hi,

I try to solve a simple algebraic equation, defined by finding the variables for which the partial derivates of 'eqn1' are all 0. I want to solve the equation for the variables x, y and lambda. Such that those three variables are expressed as a function of the other variables. In this case, i look for the solution that:

x = 0;
lambda = - m*g / 2 / y; 
y= + or - R 

How can i define such an output? Thank you for your help! (This is a simplified problem of a more complicated case.)

syms x y m g R lambda L

eqn1 = L == m*g*(y+R) + lambda * (x^2 + y^2 - R^2); 

dldx1       =diff(eqn1,x);
dldx2       =diff(eqn1,y);
dldlamba    =diff(eqn1, lambda);

dl=[dldx1 ; dldx2 ; dldlamba]

[solx, soly, sollambda]=solve(dldx1==0, dldx2==0, dldlamba==0)

Answer 1

[Jurrien Plijter]

Ah, i found it myself, you can simply define the variables for which the equation has to be solved:

[solx, soly, sollambda]=solve(dldx1==0, dldx2==0, dldlamba==0,[ x y lambda])