Expression 39: "P" Subscript, 1 , Baseline equals StartFraction, StartNestedFraction, 1 NestedOver "m" Subscript, 2 , Baseline , EndNestedFraction "M" Subscript, 1 , Baseline plus "M" Subscript, 2 , Baseline plus "m" Subscript, 2 , Baseline "E" Subscript, 1 , Baseline minus "E" Subscript, 2 , Baseline Over "m" Subscript, 2 , Baseline plus StartNestedFraction, 1 NestedOver "m" Subscript, 2 , Baseline , EndNestedFraction , EndFractionP1=1m2M1+M2+m2E1−E2m2+1m2