n = 5; 
L = randn(n,n); A = L*L'; I = eye(n); b = 1; 
cvx_begin 
	variable X(n,n) symmetric; 
    minimize( trace( I * X ) ); 
    subject to 
        trace( A * X ) == b; 
        X == semidefinite(n); 
cvx_end 
