For the symmetric matrix $A = \begin{pmatrix} 3 & 1 \\ 1 & 3 \end{pmatrix}$ with eigenvalues $\lambda_1 = 4$ and $\lambda_2 = 2$, the spectral decomposition is $A = \lambda_1 v_1 v_1^T + \lambda_2 v_2 v_2^T$ where $v_i$ are orthonormal eigenvectors. Which vector is a valid orthonormal eigenvector for $\lambda_1 = 4$?