5.3.2.23 Various problems in the space

condition: In a regular pyramid \( S A B C D \) the dihedral angle at a side edge is \( 120^{\circ} \). On the edges \( S C \) and \( S D \) the points \( K \) and \( L \) are taken, respectively, - the midpoints of these edges. Find the angle formed by the line \( D K \) with the line \( A C \).