'In so far as' and 'As far as' --Are the two conjunctions synonyms?
Solution 1:
They are not conjunctions, but idiomatic compound prepositions, and they have different meanings:
[1] As far as the weather was concerned, we were very lucky.
[2] As far as I know, he's still in Paris.
[3] Insofar as it's any business of mine I'd say they should give up.
"As far as" in [1] means "regarding", and in [2] it means "to the best of my knowledge".
"Insofar as" in [3] means "to the extent that".