R_mix at f=0 ⇒ R_B, f=1 ⇒ R_A, f=1/2 ⇒ (R_A+R_B)/2

Sympy-exact witness of the two-component isotope mixing formula at its three canonical fractions. Setup: R_mix(f) = f·R_A + (1 − f)·R_B. f = 0 (pure B): R_B exactly; f = 1 (pure A): R_A exactly; f = 1/2 (equal mixture): (R_A + R_B)/2…