The portion of the line \( 4x + 5y = 20 \) in the first quadrant is trisected by the lines \( L_1 \) and \( L_2 \) passing through the origin. The tangent of an angle between the lines \( L_1 \) and \( L_2 \) is:
If \( A \) and \( B \) are two non-zero square matrices of the same order such that: $$ (A + B)^2 = A^2 + B^2, $$ then: