Funzione logaritimica

y=log_{a}x

a = 2.2 (slider from 1 to 5, step 0.1)
g(x) = lg(x) / lg(a^(-1))
text1: "y=log_" + a + "x"
f(x) = lg(x) / lg(a)
text2: "y=log_{1/" + a + "}x"