CAS and small numbers

[Han]

When working in CAS, you are much better off using exact values. So instead of typing something like: 2.1E-10, I would recommend 21*10^(-11) as the value. Then you can convert to decimal form at the very end if needed. Most CAS will treat values having a fraction mark (in your case, a decimal point) as an implicit request to use approximate algorithms so that roundoff could possibly result in "useless" answers.