not following what it is saying

[sujoy]

okay
the thing is that this is a statement from a book which I am not getting
[underscore represents a base thus log_a[y] is log y to the base a]:
we know x = log_a[y] is a^x = y , when a>0& not equal to 1
also y>0
so if 2^t =y, we say t = log_2[y],
thus f(t) = 2^t =>f^(-1)(t) = log_2[t].....last statement
please explain the last statement
regards
Sujoy

 

[Gene]

f^-1 is used to indicate an inverse of a function.
If you don't know what they are this might help.
http://www.purplemath.com/modules/invrsfcn.htm