Exploring Rationalising the identities,
so that we can combine multiple identities. I.e. if we have f(x, y) = f(y, x)
and we have f(a, b) = g(a, b), join them to f(x, y) = f(y, x) = g(x, y). N.B. we need to then write the identity pemutor to work out that therefore g(x, y) = g(y,x).