Dear everyone can anyone help me with the euler lagrange equation which is stated in d'inverno chapter 11? in equation (11.26) it is said that when we use the hilbert-einstein lagrangian we can have: ∂L/(∂g_(ab,cd) )=(g^(-1/2) )[(1/2)(g^ac g^bd+g^ad g^bc )-g^ab g^cd ] haw can we derive this out of (11.24)? I tried to derive ∂L/(∂g_(ab,cd) ) out of (11.24), but I really don't know how to work with (∂g_(ab,cd) ? please help me!!!