use systematic trial and error to evaluate log50.
By trial and error you have to find (approximatly) such that:
or dividing by :
start with , then , which is too small,
next try , then , which is too large
So for our next try we take , then which is too small
Now we know that the required is between and , so for our next trial we use and carry on as above refining the interval containing the required solution.
CB