how do you put log1/2(9) into scientific calculator

Do you mean that the base is 1/2?

If so, use the change-of-base formula to get:  

if you want to use common logs:  log (to the base 1/2) 9  =  log(9) / log(1/2)

if you want to use natural logs: log (to the base 1/2) 9  =  ln(9) / ln(1/2)

Generally speaking, use:  log(number) / log(base)     or     ln(number) / ln(base)

You'll get the same answer using either log or ln.

Hit log then type 1/2 then (9) then enter

$${\frac{{\mathtt{log1}}}{{\mathtt{2}}}}{\mathtt{\,\times\,}}\left({\mathtt{9}}\right) = {\frac{{log}_{10}\left({\mathtt{1}}\right)}{{\mathtt{2}}}}{\mathtt{\,\times\,}}{\mathtt{9}}$$