Expression 3: "L" Subscript, 2 , Baseline equals StartFraction, "L" Subscript, 1 , Baseline Over 2 left parenthesis, 1 plus cos left parenthesis, StartNestedFraction, 2 pi NestedOver "N" , EndNestedFraction , right parenthesis , right parenthesis , EndFractionL2=L121+cos2πN