Expression 18: "E" Subscript, 1 , Baseline equals "w" tangent left parenthesis, 2 thirds tan to the negative 1st power StartFraction, "l" Over "w" , EndFraction , right parenthesisE1=wtan23tan−1lw
Expression 20: "F" Subscript, 1 , Baseline equals "w" tangent left parenthesis, 1 half tan to the negative 1st power StartFraction, "E" Subscript, 1 , Baseline Over "w" , EndFraction , right parenthesisF1=wtan12tan−1E1w