Question 301217
You can use an infinte series expansion to calculate ln(x) and then convert to log(5). 
{{{ln(x)=2*(((x-1)/(x+1))+(1/3)((x-1)/(x+1))^3+
(1/5)((x-1)/(x+1))^5+
(1/7)((x-1)/(x+1))^7+
(1/9)((x-1)/(x+1))^9)}}}
You can see the pattern and add terms depending on the accuracy you need.
Then 
{{{log(5)=ln(5)*log((e))}}}